You can use the Law of Sines to find the hypotenuse. Because it's an equilateral triangle, it's the same value for the base. If you plug in the proper angles, being 90 degrees and 60 degrees because it's an equilateral triangle, the value of the base should be 17.32050808, or 17.32 if we're rounding. If you use the usual formula for finding the area of a triangle, b * h / 2 to get an answer of 129.9 cm^2. Hope this helps and isn't too confusing! There's a bunch of lessons on Khan Academy if you need more help!
This is a bit advanced for middle school, so we might be missing some information.
