paulodamaia

a) x+9=3

x = 3 - 9

x = - 6

b) 4x=28

x = 28/4

x = 7

c) 6x=x+10

6x - x = 10

5x = 10

x = 10/5

x = 2

d) 3x-x=18-6

2x = 12

x = 12/2

x = 6