Fail = 15 boys = 1/4 of the pie or 90 degrees
Therefore, if 1/4 = 15, 3/4 = 45
b) Charlie is incorrect because you do not know how many boys and how many girls there are in Year 7. This is required to work out the answer. There may for example be 24 boys and only 5 girls. This would mean 6 boys fail the test and less than 5 girls fail the test.