for the page that starts with problems 13 and 14, it is mostly all the pythagorean therom which is a² + b² = c² (all you have to do is plug the numbers in)
in order to do this make sure you remember the longest side or the side directory across from the 90 degree angle is always c! a and b can be any of the other two sides (the legs) they just cannot be the longest side. Here’s problem 13:
a² + b² = c²
now we plug in all the numbers we have
a² + 3² = 5²
in this case i made the missing side “a”
now we must square the numbers
a² + 9 = 25
we can’t square a since we don’t have a number for it
a² + 9 = 25
-9 -9
——————
a² = 16
since we can’t add to get to the missing side like usual, we must subtract the other leg (b in this case) from c
now we must get rid of the square on the a, and because we can’t square it, the only that gets rid of a square is a square root (remember what you do to one side you must do to the other)
√a² = √16
if you don’t know how to square root on a regular calculator i suggest looking up a square root calculated (calculator soup is a pretty good reasource)
you only have to do actual math for the 16, so once you square root the 16, just cross out the square root and square on the a and you’ll get your answer
a = 4