Answer:
Step-by-step explanation: on ur graph, in a class of 90 students (20 rock, 40 hip hop, and 30 country...added = 90) , 30 chose country....30/90 reduces to 1/3.....so 1/3 chose country.
In a class of 450 students......1/3 * 450 = 450/3 = 150 chose country