Yes, these 2 equations are equivalent
The answer is C.
You need you use Pythagoras theorem 2 times to have 2 equations with the same sides i.e. for example a2 + b2 = 81 and a2 - b2 = 9.
You can do it as you have different triangles but with the same sides.
7. 233
8. 4
9. 6
10. 5
11. 4
12. 7
13. 7
B. 16.. because its in the middle
The answer to the question is A
