What is the value of x? what proportion did you set up?

These are two similar triangles.
So, a proportion can be set up to find the missing value of the side.

Since we already know one comparison, the 24 and the 8, we can put that on the right side of our proportion. And the other side can be written with the same relationship between the x and the 10.
This leaves you with:
X/10 = 24/8

Cross multiply to simplify your proportion into a regular equation.
This leaves you with:
8x = 240

Divide both sides by 8 to isolate x.
This results in:
x = 30

So, your final value for x is 30.

I hope this helps!