Just "plug n chug" as my teacher would say. In other words, replace the letters with the values.
Choice A is (7,19) which means x = 7 and y = 19. Let's replace the x and y value with these numbers in both equations. If we get a true equation, then we found the answer.
2x-y = -5 2*7-19 = -5 14-19 = -5 -5 = -5 ... true So that works. Let's try the other equation x+3y = 22 7+3*19 = 22 7+57 = 22 64 = 22 ... false So choice A is NOT the answer because of this. Let's try out choice B 2x-y = -5 2*4-9 = -5 -1 = -5 ... false so B doesn't work either. How about C? 2x-y = -5 2*8-21 = -5 -5 = -5 ... that works x+3y = 22 8+3*21 = 22 71 = 22 ... but this is false So D has to be the answer. Let's check to confirm or not 2x-y = -5 2*1-7 = -5 -5 = -5 ... true x+3y = 22 1+3*7 = 22 22 = 22 ... true BOTH equations are true at the same time so (1,7) is definitely the final answer
