Which triangle is a 30°-60°-90° triangle

Aswimming pool had 2.5 million liters of water in it. some water evaporated, and then the pool only had 22 million liters of water in it. what percent of the water evaporated?

The square pyramid has a volume of 441 cubic inches. what is the value of x? 1/7x is the height x is the base

Assume that y varies inversely with x. if y=1.6 when x=0.5 find x when y=3.2