It's 8, it gave Y so pretty easy from there on
y = 4
y = 1/4 x + 2
______________
4 = 1/4 x + 2
4 - 2 = 1/4 x + 2 - 2
2 = 1/4 x
2 × 4 = 4 × ( 1/4 ) × x
x = 8
Thus the correctly answer is option D.
