Answer:
57
Step-by-step explanation:
The midsegment is one half the length of the third side of the triangle, that is
6x + 3 = (3x + 87)
Multiply both sides by 2 to clear the fraction
12x + 6 = 3x + 87 ( subtract 3x from both sides )
9x + 6 = 87 ( subtract 6 from both sides )
9x = 81 ( divide both sides by 9 )
x = 9
Thus
midsegment = 6x + 3 = 6(9) + 3 = 54 + 3 = 57