Two. 7. 105 8. 10≤X≤ 15 9。 A = 1 10。 The answer is not unique11.4512.20.

13.5 14.- 1 15.(- 1,- 1)

Three. 16. solution: solve the inequality ①, X.

Solve inequality ①, x≤-2.

Its solution set is expressed on the number axis as:

The solution set of the original inequality group is x≤-2.

17. solution: EF‖BD.

The reason for this is the following：

In BC,

∴∠AED=∠ABC.

∵BD split ∠ABC，EF split ∠AED

∴∠AEF=∠AED,∠ABD=∠ABC.

∴∠AEF=∠ABD。

∴EF‖BD.

18. Solution: ∫∠A = 42, ∠ B = 70,

∴∠acb= 180-∠a-∠b = 180-42-70 = 68。

∫CE shares ∠ACB,

∴∠BCE=∠ACB=×68 =34。

∵CD⊥AB,∴∠CDB=90。

∴∠bcd= 180-∠CDB-∠b = 180-90-70 = 20。

∴∠DCE=∠BCE-∠BCD=34 -20 = 14。

∴∠cfd=90 ∵df⊥ce。

∴∠cdf= 180-∠CFD-∠DCE = 180-90- 14 = 76

19. solution: (1) In △CDP, ∫α= 20, β = 30,

∴∠c= 180-α-β= 180-20-30 = 130。 ∫CD‖AB，

∴∠b= 180-∠c = 180- 130 = 50；

(2) If point P is a moving point on the edge of BC, then α+β = ∠ b. 。

The reasons are as follows: ∫CD‖AB,

∴∠B+∠C = 180。

√α+β+∠C = 180，

∴∠B=α+β

20. Solution: Suppose 2 yuan bought x stamps, 5 yuan bought y stamps, and 1 yuan bought 2x stamps.

2x+x+y= 18 according to the meaning of the question.

2x+2x+5y=46。

X=4 to solve this system of equations.

y=6。

I bought six stamps with 5 yuan money.

2 1.( 1) C。

(2) 36 people whose bar chart is about 10 minutes; In the plate statistical chart, the 60 degrees that are basically not involved are about 10 minutes and 2 16 degrees. If you fill it in correctly, it will be 2 points ***6 points.

(3) In the seventh grade of this school, it is estimated that the number of people who exercise less than 20 minutes after class every day is:

×1200 =1100 (person). It is suggested that extra-curricular exercise time be increased every day, and the correct answer is 2 points.

22.( 1)△ABC graphic is correct 2 points; The area is 8, and 3 points is correct.

(2)△A 1B 1C 1 is 2 points for correct drawing, a1(4,2), b1(2,3), c1(0,0. The coordinates are correct. Three points.

23.( 1) According to question a-b=4.

2a-3b=-7。

Solution: a= 19, b= 15.

(2) If X A excavators are purchased, X B excavators are purchased (10-x).

According to the meaning,19x+15 (10-x) ≤160, and x≥0.

∴0≤x≤2.5, because x is an integer and x=0 or 1 or 2.

∴ The company has three purchase schemes:

0 sets of type A and 0 sets of type B 10; Type a 1, type b 9; 2 sets of type A and 8 sets of type B..

(3) If X A excavators are purchased, then 220x+180 (10-x) ≥1840, and the solution is x≥ 1.

It is also known from (2) that 0 ≤ x ≤ 2.5, ∴ 1 ≤ x ≤ 2.5. X =1or 2.

When x= 1,19×1+15× 9 =154 (ten thousand yuan); When x=2,19× 2+15× 8 =158 (ten thousand yuan)

∵ 154 & lt； 158,∴ scheme 1, that is, 1 one type A and nine types B are the most economical.