You found the area for the unknown lengths!?

A length doesn't have an area!

We know that the distance from the light source to the screen is 1.5 m.

Using similar triangles, we know that:

0.125/0.5 = ?/1.5

? = 37.5 cm

Then the length of the shadow becomes twice that, that is 75 cm.

Now, you do the same with the side as 10 cm.

0.10/0.5 = ?/1.5

.....