Jamila babysat nine times. she earned $15, $20, $ 10, $ 12, $20, $16, $80 and $18 for eight babysitting jobs. how much did she earn the ninth time if the mean of the data set is $24?

a is the right answer

for this case we must apply distributive property to the following expression:

the distributive property states that:

then, when applying the property we have to multiply the -2 for each term within the parenthesis: