Answer:
x= 29
Explanation:
use Pythagoras because it has a right angle and 2 sides length is given.
when the hypoteneus(side opposite the right angle) is the value you are finding out you use the equation : x²+y²=hypoteneus² (Pythagoras)
then you sub in the values you are given
(21)² + (20)² = hypoteneus²
them take the square root (²) to the opposite side to find the hypoteneus
square root (441+400) = hypoteneus
now you can put into a calculator and you get the value
hypoteneus =29 (for reference to hypoteneus is the same as X-the value you are looking for)
therefore, x=29
for extra reference, say you want to work out a side that is not the hypotenues you use the formula ,
(side u looking for)² = (hypotenues)² - (other side given)²