Let's solve for a.

r=−9+3a

Step 1: Flip the equation.

3a−9=r

Step 2: Add 9 to both sides.

3a−9+9=r+9

3a=r+9

Step 3: Divide both sides by 3.

3a

3

=

r+9

a=

1

r+3

b = 1.5

3 is it

2 is it

x5y20

x>−3y−5

x=30

4.375