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Practice, study and evaluation in the first volume of the seventh grade math class; The answer to the linear equation is on your knee ~ and so on.
3.4. 1 practical problems and linear equations of one variable (1)

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