The figure below shows an isosceles triangle XYZ, where XY = YZ. WY = 12 cm, YZ = 15 cm and XZ = 18 cm. Find the area of triangle WXY.

1. Find the length of the base XW of triangle WXY

Since triangle XYZ is an isosceles triangle with $XY = YZ$, the perpendicular line WY from Y to the base XZ bisects the base.
$XW = 18 \div 2 = 9\text{ cm}$

2. Calculate the area of triangle WXY

$\text{Area of } \triangle WXY = \frac{1}{2} \times \text{base} \times \text{height}$
$\text{Area} = \frac{1}{2} \times 9 \times 12 = 54\text{ cm}^2$