Answer:
x = 3
Step-by-step explanation:
The segment parallel to the third side and intersecting 2 sides divides those sides proportionally, that is
[tex]\frac{12-x}{x+3}[/tex] = [tex]\frac{6}{4}[/tex] ( cross- multiply )
6(x + 3) = 4(12 - x) ← distribute parenthesis on both sides
6x + 18 = 48 - 4x ( add 4x to both sides )
10x + 18 = 48 ( subtract 18 from both sides )
10x = 30 ( divide both sides by 10 )
x = 3
