Respuesta :
Answer:
The answer is 4m. I used my graphing calculator and this is how I got it step by step. Look at the pic.
Step-by-step explanation:

4
b x h / 2 = area
b x 15m / 2 = 30m^2
x2 both sides
b x 15 = 60
/15 both sides
b = 4
b x h / 2 = area
b x 15m / 2 = 30m^2
x2 both sides
b x 15 = 60
/15 both sides
b = 4