basic skill
I. 1,D 2,D 3,D 4,c。
2, 5, 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)
6、0.6X+20=0.8X- 15
X= 175