The formula for area of a triangle is 1/2 x base x height.
Let the height = x
Then the base (length) = 2x ( twice the height)
You know have 16 = 1/2 * 2x * x
Multiply both sides by 2 to remove the 1/2:
32 = 2x * x
Simplify the right side:
32 = 2x^2
Divide both sides by 2:
16 = x^2
Take the square root of both sides:
X = 4
The height is 4 units and the length is 8 Units