1) 2x - (3/7)x = 33/7

(11/7)x = 33/7

x=3

2) 9x-45= -x

9x+x=45

10x=45

x=9/2

x=4,5

3)  x-6 = 0  ;  4x-6 = 0

x=6

x=3/2

x1 = 3/2 ; x2 = 6

x1 = 1,5 ; x2 = 6