20 - k/15 = 17
20 - 17 = k/15
3 = k/15
k = 45
C
the square of the sum of 7 times x and 3 is expressed as
7x + 3 ← the sum of 7 times x and 3
(7x + 3)² ← the square of the sum of 7 times x and 3
4 times the difference of x and 1 is expressed as
x- 1 ← the difference of x and 1
4(x - 1) ← 4 times the difference of x and 1
putting it all together gives
(7x + 3 )² / 4(x - 1 ) → C