The answer to this question would be: C.5x = 5
In this question, you got two equation which was:1st: 2x + y = 3
2nd: x - 2y = -1
You are asked to multiply one of the equation and add it. If you multiply the first equation, the number of y would be same so the y variable will be removed. If you multiply the second equation, the number of x would be same so the x variable will be removed.
In the answer, all variable that used is x, so the one you need to multiply should be the first equation(removing y with result with x)
4x + 2y = 6
x - 2y = -1
__________+
5x +0y = 5