The problem is simply a conversion problem. So, we need a conversion factor to change from one unit to another unit. To do this, we need a conversion factor which would relate the different units involved. We either multiply or divide this certain value to the original measurement depending on what is asked. From the problem, we use 1 yard is equal to 0.914 meters. We do as follows:
20.0 cubic yards ( 0.914 meters / 1 yard )^3 = 15.27 m^3