basic skill

a， 1，

D

2、

D

3、

D

4、

C

Two, five,

275

6、250

7、 175,250,500 1, 1 175

3.8. Let's assume that the cost price of each of these jackets is X yuan.

X( 1+0.5)*0.8=60

X=50

9. Let the original price be X yuan.

x * 0.8( 1-0. 1)= 144

X=200 (yuan)

Expansion and improvement

I. 1，a

2、B

2, 3, 1.5

4、( 1)3,3,5.8; 3,3,6

(2)②

3, 5, ( 1)39, 22, 858

(2)38,24,9 12

(3)(40-X)，(20+2X)，(40-X)*(20+2X)，(4)(40-X)*(20+2X)= 1200

6、0.6X+20=0.8X- 15

X= 175

7. Add 10 sets.

good