Explanation:
The total no of pieces is 35. Let Gwen has B black pieces and R red pieces.
(a) She bought 4 times as many red pieces as she did black pieces. It means,
Red pieces = 4B
Equations that represents the number of pieces of each kind of licorice that Gwen bought are :
R + B = 35 ....(1)
and
R = 4B ....(2)
((b) Put equation (2) in equation (1)
4B + B = 35
5B = 35
B = 7
Put the value of B in equation (2)
R = 4(7) = 28
(c) There are 7 black and 28 red pieces of licorice.