Question 114006
7.50L+3S=97.50
L+S=25 OR L=25-S.
NOW SUBSTITUTE (25-S) FOR L IN THE OTHER EQUATION & SOLVE FOR S.
7.50(25-S)+3S=97.50
187.5-7.5S+3S=97.50
-4.5S=97.50-187.50
-4.5S=-90
S=-90/-4.5
S=20 THE NUMBER OF SMALL BOXES BOUGHT.
25-20=5 LARGE BOXES BOUGHT.
PROOF
7.50*5+3*20=97.5
37.5+60=97.5
97.5=97.5