For this one you want to cancel out the x-terms.
Multiply top equation by -2
---> -2x -10y = 6
---> 2x +7y = 3
Add them together
---> -3y = 9
Solve for y ...
Answer:
2500+6% per year for 3 years would be 2950.
-2(x+7)+3=19
-2x-14+3=19
-2x-11=19
-2x=8
x=4
D, because two negative signs next to each other means to add so its pretty much 7/8+1/8 which equals 8/8 which also equals 1