Solution: x( 1-0.8)=9.

0.2x=9

x=45

0.5x-2=24

Solution: 0.5x=22

x=44

2x-6.8=3.5

Solution: 2x= 10.3

x=5. 15

3x-2.8=2

Solution: 3 times =4.8

x= 1.6

5x-3.9=5. 1

Solution: 5x=9

x= 1.8