Answer:
x = 11
Explanation:
The line parallel to the base line and intersecting the other 2 sides divides those sides proportionally, thus
=
( cross- multiply )
6(3x + 7) = 240 ( divide both sides by 6 )
3x + 7 = 40 ( subtract 7 from both sides )
3x = 33 ( divide both sides by 3 )
x = 11