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