Answer:
x = 11
Step-by-step explanation:
The line parallel to the base line and intersecting the other 2 sides divides those sides proportionally, thus
[tex]\frac{6}{48}[/tex] = [tex]\frac{5}{3x+7}[/tex] ( 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
