90 - 7 x 5 - 24 ÷ 3 x 5
= 90 - 35 - 8.0 x 5
= 90 - 35 - 40
= 55 - 40
= 15

Therefore, 90 - 7 x 5 - 24 ÷ 3 x 5 = 15.