G = Gumdrops (in pounds)
C = chocolate (in pounds)
Since the mixture was 60 pounds,
G + C = 60
We also know that gumdrops sell for 60 cents per pound and chocolate sells for 52 cents per pound. And the combined mixture, 60 pounds will sell for 54 cents per pound.
.6G + .52C = (60)(.54) = 32.4
Since G + C = 60
G = 60 - C
Substituting this in the other equation
.6(60-C) + .52C = 32.4, with only one variable, C
36 - .6C + .52C = 32.4
Combine and rearrange terms
3.6 = .08C
C = 45
The mixture contain 45 pounds of chocolate and 15 (60-45) pounds of gumdrops.