1.C

2.D

3.C

4.C

5.A

6.-2 \ 3 x = 4 ^ 2

7.( 12+ 13)x = 300 12

8.2

9.-5x 2 5x 7 -8x - 16 -8 2

10. solution: x=-3 x=3\8 x=3.5 x=6/5.

1 1. Solution: Let a pair of people with x 3x-4-x= 120.

x=3 1

3×3 1-4=89 (person)

12. Solution: Let the original price of 20 copies be x yuan x-80%x= 1.6.

x=8

8÷20=0.4 (yuan)