The answer is letter d. The Fibonacci Sequence states to add the 2 previous number to get the next number starting with 1. So, 1 + 0=1, 1+1=2, 1+2=3, 2+3=5,3+5=8, 5+8=13, etc....
I added 13+21 to get 34. Then add 21+34 to get 55. Then add 34+55 to get 89.
7x+3y=-1
x+y=-3
8x+4y=-4
2x+y=-1
y=-1-2x
x+y=-3
x-1-2x=-3
-x=-2
x=2
y=-1-2*2=-1-4=-5
15 is your percentage to the answer