1.x-2 x+2 (x-2)+x+(x+2)=66

2.(3+a) 3+a=3*(9-3)

3. Solution: Let Class Two plant trees x =102 *10+1= 21.

4.X=20

5.x= 100

6.( 1)x=4 (2)280

5.3(3)

1.7.2

2.6

3.20

4.5000

5.48

6.( 1)7

(2)400