1) 9b + 6b - 15 = 615

2) 17x - x + 5x-19 = 170

3) (x - 23) : 26 = 8

4) 1728 : (56-x) = 36

1) 9b + 6b - 15 = 615 2) 17x - x + 5x - 19 = 170 3) (x - 23) : 26 = 8

15b = 615+15 21x = 170 + 19 x - 23 = 26 * 8

15b = 630 21x = 189 x - 23 = 208

b = 630 : 15 x = 189 : 21 x = 208 + 23

b = 42 x = 9 x = 231

4) 1728 : (56 - x) = 36

56 - x = 1728 : 36

56 - x = 48

x = 56 - 48

x = 8