Answer:
9
Step-by-step explanation:
The ratio of 5 to 5+3 is equivalent to the ratio of 15 to 15+x. This is because when you have a triangle inside of a triangle and both of them share two of the same sides and the third sides are parallel to each other, the side ratios of the triangles are always proportionate.
[tex]\frac{5}{5+3} =\frac{15}{15+x}[/tex] Starting equation
[tex]\frac{5}{8} =\frac{15}{15+x}[/tex] Simplify
[tex]5(15+x)=8*(15)[/tex] Cross multiply
[tex]75+5x=120[/tex] Distributive Property on left and simplify on right
[tex]5x=45[/tex] Isolate the variable
[tex]x=9[/tex] Divide both sides by 5 (Division Property of Equality)
