We are given
The average income, I, in dollars is

(a)
now, we are given
average income is $275000
so, 
now, we can set them equal
and then we can solve for x


we will have to use quadratic formula


we get


we need to find youngest age
It means that we need to choose smallest value
so,
............Answer
(b)
we are given
x=40
so, we can plug it and find I

..............Answer
12 times 4 minus 3 because the 12 represents how much is in each of the 4 cases and you minus that by 3 and you get your answer
The word numerous means many. If there are numerous errors in a paper then there are many errors.