Formula for area of a triangle:
A = [tex] \frac{1}{2} [/tex] * base * height
You are already given two out of three variables of the formula.
128 = [tex] \frac{1}{2} [/tex] * 16 * height
Multiply 2 to both side and divide both side by 16
[tex] \frac{128 * 2}{16} [/tex] = height