Question

How would I solve this?

Answer 1

The criterion is that:

The ratio of corresponding sides of both triangles are the same.

8/24 = 1/3

4/12 = 1/3

12/36 = 1/3

So both triangles are similar, because ratio of corresponding sides are the same.

Answer 2

The triangles are similar by SSS similarity criterion:
Let, the first triangle = Δ ABC
Second triangle = Δ PQR

then, Δ ABC = 3 × Δ PQR

Their sides are proportional to each other, and gives three when dividing smaller triangle side with corresponding side of larger triangle

Hope this helps!