The Randolph’s used 12 more gal of fuel oil in October than in September and twice as much oil in November as in September. If they used 132 gal for 3 months, how much was used during each month?
Let the usage in the three months be S, O and N.
O = S + 12
N = 2S
S+O+N = S + S + 12 + 2S= 132
3S = 120
Solve for S.
The use the O and N equations to get the others.