document.write( "Question 644020: After a student wrote a $1,400 check to pay for a car, he had a new balance of $700 in his account. What was the account balance before he wrote the check?\r
\n" ); document.write( "\n" ); document.write( "$2,100 is the amount but on my online home work it has this:\r
\n" ); document.write( "\n" ); document.write( "x − 1,400 + what = 700 + 1,400 \r
\n" ); document.write( "\n" ); document.write( "I put 700 but they said I was wrong \n" ); document.write( "

Algebra.Com's Answer #404781 by KMST(5328) $\"\"$ $\"About$

You can put this solution on YOUR website!
The expected answer is $\"highlight%281400%29\"$ .
\n" ); document.write( "That is what you have to add to both sides of the equal sign as a first step to solve the $\"x-1400=700\"$ equation you would start with (calling the initial balance that you have to find $\"x\"$ ).
\n" ); document.write( " $\"x-1400=700\"$ --> $\"x-1400%2B1400=700%2B1400\"$ --> $\"x=2100\"$
\n" ); document.write( "
\n" ); document.write( "The computer grading your homework may accept only \"1400\", only \"1,400\" or both.
\n" ); document.write( "(My son went through an online school, so I know the format of your answer often matters).
\n" ); document.write( "
\n" ); document.write( "What they are trying to do is train you to solve equations by following a fixed procedure.
\n" ); document.write( "With some luck, you will understand the situations described and see the logical way to solve problems, rather than blindly following a procedure.
\n" ); document.write( "The procedure to solve an equation that has $\"x\"$ on only one side of the equal sign works like this:
\n" ); document.write( "Step 1 - write an equation to describe the information you have.
\n" ); document.write( "You would write $\"x-1400=700\"$ to describe that starting with a balnce of $\"x\"$ ,
\n" ); document.write( "after spending (subtracting) $\"1400\"$ from that, you got $\"700\"$ left.
\n" ); document.write( "Step 2 - Undo what was done to that $\"x\"$ step by step, and in reverse order, but to keep the equal sign valid you must do the same thing to both sides of the equal sign.
\n" ); document.write( "On the left hand side there is $\"1400\"$ subtracted from $\"x\"$ . So you add $\"1400\"$ to both sides, because if that equal sign was valid, it will still be valid after adding the same number to both sides (and viceversa).
\n" ); document.write( "
\n" ); document.write( "If you had a more complicated equation, like $\"3x%2B2=17\"$ , you would reason that the $\"x\"$ would have been multiplied times $\"3\"$ first, and that $\"2\"$ was added after that.
\n" ); document.write( "Your solution would look like this
\n" ); document.write( " $\"3x%2B2=17\"$ --> $\"3x%2B2-2=17-2\"$ (undoing the adding of $\"2\"$ )
\n" ); document.write( " $\"3x%2B2-2=17-2\"$ --> $\"3x=15\"$ (simplifying and calculating as you can on both sides)
\n" ); document.write( " $\"3x=15\"$ --> $\"3x%2F3=15%2F3\"$ (dividing by $\"3\"$ to undo the multiplication times $\"3\"$ )
\n" ); document.write( " $\"3x%2F3=15%2F3\"$ --> $\"x=5\"$ (simplifying and calculating as you can on both sides). \n" ); document.write( "

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