The answer is D) you could multiply A by -4 and B by 5,
This choice would help you cancel out the x variable so that you could solve for the y. To see this, multiply the x terms by the given amounts.
Equation A (just the x)
5x ----> multiply by the -4 above
5x * -4 = -20x
Equation B (just the x)
4x -----> multiply by the 5 above
4x * 5 = 20x
Since -20x and 20x cancel when adding, these are the numbers that you are looking for.