2.B

3.D

4.y = 10-3x x = 10-y y = 4y = 1 1x = 8/3。

5. The solution is because x= 1 y=2.

So 3* 1+2a=- 1.

So 3+2a=- 1.

So 2a-4

Get a =-2.

6.5x+5=3y

Solution 5x=3y-5

X= 3/5 y-5 is obtained.

x=5 y= 10

7.x= 10 y=0

x=8 y= 1

x=6 y=2

x=4 y=3

x=2 y=4

x=0 y=5

A: Six plans, three for five dollars can't be done.