Fill two of the pools with water, each pool will be filled to a depth of 5 feet. the other necessary dimensions are given below. how much water is necessary for each of the elements below?
the isosceles triangle pool: height 20ft and base 35ft
the equilateral triangle pool: height 52ft and base 60ft

Find the volume of each pool. The formula for triangular prisms is length*width*height*1/2. Or, since your numbers give the base, you can just multiply the height and the base, then multiply by 5, then divide by 2 to get the answer.
So, 20*35*5/2 = 1,750 ft³ is the equation for the isosceles triangle, and the equilateral triangle pool is 52*60*5/2 = 7,800 ft³.
The volume = how much water you need for each pool.
Hope that answered your question.