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