Answer:
[tex]\boxed{\boxed{x=4}}[/tex]
Step-by-step explanation:
If the triangles are similar, then the sides are in proportion.
We have the equation:
[tex]\dfrac{3x+8}{4}=\dfrac{15}{3}[/tex] cross multiply
[tex]3(3x+8)=(4)(15)[/tex] divide both sides by 3
[tex]3x+8=(4)(5)[/tex]
[tex]3x+8=20[/tex] subtract 8 from both sides
[tex]3x=12[/tex] divide both sides by 3
[tex]\boxed{x=4}[/tex]
