The statement at the top says that the triangles are 'similar'. That means that the corresponding angles are equal, and each pair of corresponding sides have the same ratio. From the 4 and the 8, you can see that each side in the small one is 1/2 the length of the corresponding side in the big one. So the missing sides are 1/2 the length of the 7 and the 12.
I’m not sure tbh,but you can use the app photomath and it should tell you!
R= 5
(2-6). -4
—— = ——-
(4-r). (This has to be -1 for the answer to be 4)
4-5=-1
So r=5
