Verified Answer :

twvogels

The therorem is: 

\(a^{2} + b^{2} = c^{2}\)
or, solving for b:
\(b = \sqrt{c^{2}-a^{2}}\)

\(b = \sqrt{20^{2}-15^{2}}\)
\(b = \sqrt{400-225}\)
\(b = \sqrt{175}\)
\(b \approx 13.23\)

apologiabiology

so if you have a right triangle with legs legnth a and b
and a hypotonuse legnth c, then
a^2+b^2=c^2

given in the comments is that
a=15
c=20
input and solve
15^2+b^2=20^2
225+b^2=400
subtract 225 from boths ides
b^2=175
take square root of both sides
b=5√7

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