SSS - the side they're sharing is also congruent so if you just add in the other congruent sides you get SSS
3:8 is equivalent to 12:32 multiplying by 3 to 12 is 4, so you multiply each number to 4. 3 x 4 = 12 8 x 4 = 32 yes 3:8 is equal to 12:32.
It would be 5sqrt2
a^2 + b^2 = c^2
5^2 + 5^2 = c^2
25 + 25 = c^2
50 = c^2
c = sqrt 50
c = 5sqrt2