Answer:
10.4
Step-by-step explanation: Given that;
perimeter p = 70.6 km
longer base b1 = 20.2 km
smaller base b2 = 8.8 km
The two remaining sides have the same length
I apply the formula:
L = P - ( b1 + b2)
L = [70.6 - ( 20.2 + 8.8 )]/2
L = 41.6/2 = 20.8
Since the two remaining sides have the same length
L/2 = 20.8/2 = 10.4