Question

2x + y = 3

Answer 1

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

Answer 2

The answer is c you can see this instantly because if you multiply equation one by 2 it will start with 4x. add x that is on the other equation and  u get 5x, there is only one option with x and that s C