The most common shapes in geometry-related problems are lines, triangles, rectangles, squares, circles, parallelograms, rhombus, and trapezoids. Sometimes it involves common solids like spheres, cylinders, rectangular parallelepiped, and cubes.

**Example**

An isosceles triangle has an altitude equal to 12 inches and a perimeter equal to 36 inches. Find the length of the base and the length of the equal sides.

**Solution**