Answer: 60
Explanation:
You have to use Pythagorean Theorem because the other side is not listed of the triangle
Pythagorean Theorem: a² + b² = c²
a² + 20² = 25²
a² + 400 = 625
625-400 = a²
a² = 225
Find the square root of 225 to find the missing length
= 15 (this is the missing length for QS
To find the perimeter, add all the sides...
15 + 20 +25 = 60