Answer:
6.6 cm.
Step-by-step explanation:
The area of a trapezium A = (h/2)(a + b) where h = the height, a and b are the length of the parallel sides.
So substituting the given values in this formula:
34 = (4/2)(10.4 + b)
34 = 2(10.4 + b
34 = 20.8 + 2b
2b = 34 - 20.8 = 13.2
b = 6.6 cm.