The hypotenuse c = 14, length of a = 9 and length b = ?.
\Apply pythagorean theorem:
.
(Substitute a = 9, and c = 14)
Evaluate powers:
.

Apply subtraction property of equality: a = b then
.
(Subtract 81 from each side)
Apply commutative property of addition: a + b = b + a.
\
(Apply additive inverse property:
)
(Subtract:
)
Apply square roots property:
then
.

The positive value of 
The length of
.