Answer:
4 miles
Explanation:
Formula for calculating the area of a trapezoid is expressed as shown;

a and b are the length of the bases of the trapezoid and h is its height
Given a = 1.2miles, b = 2.4miles, Area = 7.2 square miles
Substituting this values into the formula to get the height;
7.2 =


The height of the trapezoid is 4miles