Okay. The question is m/9 - 17 = 21. First off, we will add 17 to both sides. -17 + 17 cancels out. 21 + 17 is 38. That leaves m/9 = 38. Multiply each side by 9 to isolate the m, because m is the numerator and 9 is the denominator. m/9 * 9/1 cancels out. 38 * 9 is 342. Let's check this. 342/9 is 38. 38 - 17 is 21. 21 = 21. There. x = 342.
You want to try and get rid of one of the variables ( x or y) so you would multiply the second equation by 2 which would make the x variable -2x which then when added to the first equation would eliminate the x variable.
Answer: c. Multiply the second equation by 2.
