1) 90 - (42 + 8) = 90 - 50 = 40
2) (58 - 50) + 7 = 8 + 7 = 15
3) 39 - (17 - 8) = 39 - 9 = 30
4) (13 + 7) - 9 = 20 - 9 = 11
1) 90 - (42 + 8) = 90 - 50 = 40
2) (58 - 50) + 7 = 8 + 7 = 15
3) 39 - (17 - 8) = 39 - 9 = 30
4) (13 + 7) - 9 = 20 - 9 = 11