First, you put the triangles in a ratio
Then, you ask yourself "what do I have to divide seven by to get 5" so you do 7.5/5 to get that answer (which is to divided by 1.5)
Then, on the other side, you divide 22.5 by 1.5 as well
Then, you ask yourself "what do I have to divide seven by to get 5" so you do 7.5/5 to get that answer (which is to divided by 1.5)
Then, on the other side, you divide 22.5 by 1.5 as well