ANSWER
x = 3
AB = 22
EXPLANATION
We have that M is the midpoint of AB.
Since that is the case, then:
AM = MB
We have that:
AM = 3x + 2
MB = 7x - 10
So:
3x + 2 = 7x - 10
Collect like terms:
7x - 3x = 2 + 10
4x = 12
x = 12 / 4
x = 3
To find the length of AB, we simply find AM or MB and double it, since:
AB = 2AM = 2MB
AM = 3(3) + 2 = 9 + 2
AM = 11
=> AB = 2 * 11
AB = 22
