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)