2 • xy (midsegment) = sum of the bases
Plug in the numbers
2 • 12.5 = 3x + 1 + 15
Add 1 and 15 together
25 = 3x + 16
Subtract 16 on both sides and you should get:
9 = 3x
Divide both sides by 3
9/3 = 3x/3
Answer:
3 = x
