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
It will be 1 of the 100block
5 of the tens block and 2 single
1.0g/cm3 means that the mass of one cm3 is 1.0g
The easiest method to use is the rule of three, and let x be the mass of 10.0 cm3 of water
1g -- > 1.0 cm3
x --> 10.0 cm3
x= (10*1)/1
x=10.0 g
So the mass of 10.0 cm3 of water is 10.0g
Hope this Helps! :)