Answer:
The answer is below
Explanation:
A triangle is a polygon with three sides and three angles. Types of triangles are acute, obtuse, isosceles, equilateral, scalene and right angled triangle.
A right angled triangle is a triangle in which one of the angles is 90°. In a right angled triangle, the longest side is known as the hypotenuse and the side is opposite to the right angle.
Pythagoras theorem states that the square of the hypotenuse is equal to the sum of the square of the other two sides.
Given the question attached, using Pythagoras theorem:
18² = x² + 12²
324 = x² + 144
x² = 180
x = 13.42