15. 
Add "g" on both sides
Multiply 5 on both sides to get x by itself
x = 5(a + g)
x = 5a + 5g
18. a = 3n + 1
Subtract 1 on both sides
a - 1 = 3n
Divide 3 on both sides to get n by itself
= n
21. M = T - R
Add "R" on both sides to get "T" by itself
M + R = T
24. 5p + 9c = p
Subtract "5p" on both sides
9c = p - 5p
9c = -4p
Divide 9 on both sides to get "c" by itself
c = 
or c = 
27. 4y + 3x = 5
Subtract "4y" on both sides
3x = 5 - 4y
Divide 3 on both sides to get "x" by itself
x = 
x = 
If you look through the chart, you'll see that in each column,
the amount of money donated is 1/5 the number of lunch
specials sold.
The equation is:
Donation amount = (1/5) · (lunch specials sold) .
The constant of proportionality in money per lunch special sold
is $1/5 or 20 cents.
We have that
the first balance indicates--------> 10 g
the second balance indicates--------> 0 g
the third balance indicates--------> 7.5 g
therefore
the <span>mass of the chick is (10+0+7.5)----> 17.5 g
the answer is
17.5 g</span>
