8. Suppose that the per capita income of farmers in this township was X yuan last year.

( 1+20%)x = 1.5x- 1200

The solution is x=4000.

Last year, the per capita income of farmers in this township was 4000 yuan.

9. Set another section as xcm.

x+2x-5= 100

The solution is x=35.

So 2x-5=65.

A: It should be sawed 35 cm away from the club head. (or at 65 cm)

10. It's cost-effective to buy a card for X yuan.

x( 1-8/ 10)>200

Solution x > 1000.

A: When the shopping expenses exceed 1000 yuan, it is cost-effective to buy a card for shopping.