document.write( "Question 72059: The sum of n and three subtracted from twelve times n is the same as negative eleven plus the product of 2 and the difference of n and five. \n" ); document.write( "
Algebra.Com's Answer #51520 by bucky(2189)![]() ![]() ![]() You can put this solution on YOUR website! This is as much an exercise in interpreting the wording of this problem as it is doing the \n" ); document.write( "math work to solve it. Let's start with the first part: \n" ); document.write( ". \n" ); document.write( "\"The sum of n and three subtracted from twelve times n\" \n" ); document.write( ". \n" ); document.write( "This is not clearly written. I could interpret this two ways. The first way is that I \n" ); document.write( "could assume that n is first added to 3 and that result is subtracted from 12 times n. \n" ); document.write( "Written in algebraic form this would be 12*n - (n + 3) \n" ); document.write( ". \n" ); document.write( "But I could also interpret this as twelve times n is 12*n and three subtracted from that \n" ); document.write( "is (12*n - 3). Then add n to that to get n + 12*n - 3 which simplifies to 13*n - 3 \n" ); document.write( ". \n" ); document.write( "I'm going to assume the first one is what they intended and they wanted you to use. But it \n" ); document.write( "would be much better if they had said \"from the product of 12 and n subtract the quantity \n" ); document.write( "resulting from the sum of n and 3. It is important that math equations be clearly stated \n" ); document.write( "to avoid misunderstandings. \n" ); document.write( ". \n" ); document.write( "12*n - (n + 3) \n" ); document.write( ". \n" ); document.write( "and this simplifies to 12*n - n - 3 which reduces to 11*n - 3 \n" ); document.write( ". \n" ); document.write( "The next part of the problem says \"is the same as\" which really means \"is equal to\". So \n" ); document.write( "we now have 11*n - 3 = ???? Now we need to interpret what the problem says after the \n" ); document.write( "\"is the same as\" wording. \n" ); document.write( ". \n" ); document.write( "The next thing the problem says is \"negative eleven plus the product of 2 and the difference \n" ); document.write( "of n and five\". This is more clear than the statement describing the operations on the other \n" ); document.write( "side of the equation. Let's start at the end and work backwards. The difference of n and 5 is \n" ); document.write( "written as (n - 5). The product of 2 and that term is 2*(n - 5). Then we add negative 11 \n" ); document.write( "to that and the whole expression is -11 + 2*(n - 5) \n" ); document.write( ". \n" ); document.write( "This now makes our equation: \n" ); document.write( ". \n" ); document.write( "11*n - 3 = - 11 + 2*(n - 5) \n" ); document.write( ". \n" ); document.write( "Multiply the 2 times the (n - 5). When you do you get 2*n - 10. Substitute this into the \n" ); document.write( "equation and you get: \n" ); document.write( ". \n" ); document.write( "11*n - 3 = - 11 + 2*n - 10 \n" ); document.write( ". \n" ); document.write( "On the right side combine the - 11 and -10 to get -21 and make the equation: \n" ); document.write( ". \n" ); document.write( "11*n - 3 = 2*n - 21 \n" ); document.write( ". \n" ); document.write( "Get rid of the -3 on the left side by adding +3 to both sides. This addition results in: \n" ); document.write( ". \n" ); document.write( "11*n = 2*n - 18 \n" ); document.write( ". \n" ); document.write( "Finally, eliminate the 2*n on the right side by subtracting 2*n from both sides to get: \n" ); document.write( ". \n" ); document.write( "9*n = -18 \n" ); document.write( ". \n" ); document.write( "Now all you have to do is divide both sides by 9 to get n = -18/9 = -2. \n" ); document.write( ". \n" ); document.write( "Perhaps the most important lesson to be learned from this (in addition to the fact that \n" ); document.write( "it's easy to think you have said something clearly when you have not) is the importance \n" ); document.write( "of writing things so that there is little chance for misunderstanding. Hope this helps \n" ); document.write( "you to understand the problem and enables you to argue with your teacher if he or she \n" ); document.write( "elected the other interpretation for the left side of the equation. [The other interpretation \n" ); document.write( "does not give a nice even answer like n = -2.] \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " |