b = 3h . . . . . . . .given by the problem statement
A = (1/2)bh . . . . formula for the area of a triangle
486 cm² = (1/2)*(3h)*h . . . substitute given information
(2/3)*486 cm² = h² . . . . . .multiply by 2/3
√324 cm = h . . . . . . . . . . . . . .take the square root
The height is 18 cm.
The base is 3*18 = 54 cm.
