5x2 - 15 ÷ y - (6 + 15)

To find the value of the expression when x = 5 and y = 5, we substitute those values into the expression:

5x2 - 15 ÷ y - (6 + 15)
= 5(5)2 - 15 ÷ 5 - (6 + 15)
= 5(25) - 15 ÷ 5 - 21
= 125 - 3 - 21
= 101

Therefore, when x = 5 and y = 5, the value of the expression is 101.