Given the triangle with two sides given, we are asked to find the unknown side which is x.
Using pythagoras theorem:
recall that:
a² + b² = c²
a² = c² - b²
So, let:
b = 10
c = 14
a = x
x² = 14² - 10²
x = √(14)² - (10)²
x = √196 - 100
x = √96
x = 9.79