Okay, so since you know the side lengths of the rhombus and the formula for area it shouldn't be too hard.
A = base x height or just A = b x h.
Base of the rhombus is 18 1/2 m, or 18.5.
Height of the rhombus is 18 m.
18.5 x 18 = 333
The area is 333

Hope I could help!!