Can someone check over these problems for me?

Question

1. The width of a rectangle is fixed at 28 cm. What lengths will make the perimeter greater than 70 cm?
A: the length must be greater than 7 cm.

2. 7x=-63
A: x=-9

3. Is (-8.-9)a solution of 2x+4y=12
A: No

4. -1/2x=-9/10
A: 9/5

5. Solve the system of equations
x+3y=7
x=8-3y
A: No solution

6. find slope
(9,8)
(10,-7)
A:-15

Answer 1

correct.

Answer 2

thank you!

Answer 3

pls solve 3x10=(2x10)+(1x_)