Answer:
MB = 21
Step-by-step explanation:
If M is the midpoint of AB, then AM = MB
AM + MB = AB
AM + AM = AB
Replace with AM = 3x+3 and AB = 8x-6
3x+3 + 3x+3 = 8x-6
Combine like terms
6x +6 = 8x-6
Subtract 6x from each side
6x-6x +6 = 8x-6x-6
6 = 2x-6
Add 6 to each side
6+6 = 2x-6+6
12 = 2x
Divide by 2
12/2 = 2x/2
6 =x
Now we want to find MB = AM
MB = AM
MB = 3x+3
= 3(6) +3
= 18+3
=21
