document.write( "Question 1131188: The sum of three numbers is 15. The sum of twice the first number, 4 times the second number, and 5 times the third number is 49. The difference between 3 times the first number and the second number is 16. Find the three numbers. \n" ); document.write( "
Algebra.Com's Answer #747815 by ankor@dixie-net.com(22740)![]() ![]() You can put this solution on YOUR website! The sum of three numbers is 15. \n" ); document.write( "a + b + c = 15 \n" ); document.write( " The sum of twice the first number, 4 times the second number, and 5 times the third number is 49. \n" ); document.write( "2a + 4b + 5c = 49 \n" ); document.write( " The difference between 3 times the first number and the second number is 16. \n" ); document.write( "3a - b = 16 \n" ); document.write( ": \n" ); document.write( " Find the three numbers. \n" ); document.write( ": \n" ); document.write( "Add the 1st and the 3rd equations \n" ); document.write( "a + b + c = 15 \n" ); document.write( "3a -b + 0 = 16 \n" ); document.write( "-----------------adding eliminates b \n" ); document.write( "4a + 0 + c = 31 \n" ); document.write( "4a + c = 31 \n" ); document.write( ": \n" ); document.write( "multiply the 1st equation by 4 and subtract the 2nd equation \n" ); document.write( "4a + 4b + 4c = 60 \n" ); document.write( "2a + 4b + 5c = 49 \n" ); document.write( "-------------------subtraction eliminates b \n" ); document.write( "2a + 0 - c = 11 \n" ); document.write( "2a - c = 11 \n" ); document.write( ": \n" ); document.write( "Add the two resulting equations \n" ); document.write( "4a + c = 31 \n" ); document.write( "2a - c = 11 \n" ); document.write( "----------------adding eliminates c, find a \n" ); document.write( "6a + 0 = 42 \n" ); document.write( "a = 42/6 \n" ); document.write( "a = 7 \n" ); document.write( ": \n" ); document.write( "use the 3rd equation to find b \n" ); document.write( "3a - b = 16 \n" ); document.write( "3(7) - b = 16 \n" ); document.write( "-b = 16 - 21 \n" ); document.write( "-b = -5 \n" ); document.write( "b = 5 \n" ); document.write( ": \n" ); document.write( "Find c using the 1st equation \n" ); document.write( "7 + 5 + c = 15 \n" ); document.write( "c = 15 - 12 \n" ); document.write( "c = 3 \n" ); document.write( ": \n" ); document.write( ": \n" ); document.write( "Chck solutions in the 2nd equation \n" ); document.write( "2(7) + 4(5) + 5(3) = \n" ); document.write( "14 + 20 + 15 = 49 \n" ); document.write( " \n" ); document.write( " |