The formula of getting the volume of a regular prism is L x W x H = V.
Given: V: 7.35m3
L: 4.2 m
H: 50 cm (Convert this to meters) = 0.5m
W: ?
L x W x H = V
4.2 x W x 0.5m = 7.35m3
2.1m2 x W = 7.35m3 <-- Divide both sides by 2.1m2
The result would be W= 3.5m
So the width of the pond is 3.5m
Hope this solution helps you!