the side length of the third side is 16
Step-by-step explanation:
The triangle is right angled. So we would apply pythagoras' theorem:
Hypotenuse² = opposite² + adjacent²
Hypotenuse = longest side = 20
adjacent = 12
opposite = ?
20² = opposite² + 12²
400 = opposite² + 144
400 - 144 = opposite²
opposite² = 256
opposite = √256
opposite = 16
Hence, the side length of the third side is 16