Answer:
20
Step-by-step explanation:
which side is x ? the Hypotenuse - the side opposite of the 90 degree angle ? or is it one side touching the 90 degree angle ?
that is important. we need to know which side is the Hypotenuse to make the right calculations.
if I assume x is the Hypotenuse, then the calculation follows Pythagoras like this
x² = 12² + 16² = 144 + 256 = 400
x = sqrt(400) = 20
but just in case, if x is a side touching the 90 degrees angle, then the would look like this (depending on which of the other sides is the Hypotenuse)
either
12² = 16² + x²
144 = 256 + x²
-112 = x²
that did not work. a square root of a negative number did not work for actual distances.
or
16² = 12² + x²
256 = 144 + x²
112 = x²
x = sqrt(112) = 10.58
