Height ##=12 cm##

The area of a triangle can be determined with the equation ##

area = 1/2 * base * height##

Find the area of the first triangle, by substituting the measurements of the triangle into the equation.

##Areatriangle = 1/2 * 18*10##

## = 90cm^2##

Let the height of the second triangle ##=x##.

So the area equation for the second triangle ##=1/2*15*x##

Since the areas are equal,

##90 = 1/2 * 15*x##

Times both sides by 2.

##180 = 15x##

##x=12##