This is the question that's gonna put me over the top and make me a Brainly Genius. Of course working for free doing middle school math homework doesn't really sound like a genius, but I'm doing it anyway.
This one is the Pythagorean Theorem of course:



The Shakespeare Quadratic Formula (2b or -2b) is a little shortcut for the quadratic formula when the middle term is even.

So we get

The minus root is less than -6 giving negative sides, so we reject it and conclude

Choice C
When I hit Add I officially become a Genius. Maybe I should retire.
Answer:
1. 21
2. 896
3. 20.9
Step-by-step explanation:
Use BODMAS/BIDMAS to solve.