To figure out which value of y makes this true, plug in each option:
y = 8
25 - y < 15 Plug in 8 for y
25 - 8 < 15
17 < 15 This is false because 17 is not less than 15
y = 9
25 - y < 15 Plug in 9 for y
25 - 9 < 15
16 < 15 This is false because 16 is not less than 15
y = 10
25 - y < 15 Plug in 10 for y
25 - 10 < 15
15 < 15 This is false because 15 can't be less than itself (15)
y = 11
25 - y < 15 Plug in 11 for y
25 - 11 < 15
14 < 15 This is true because 14 is less than 15
Your answer is D