The balance of Alicia' s account in 7 years
=$39446.78
=B
S=number of 6 cent stamps
t=number of ten cen stamps
e=number of 8 cent stamps
w=number of 20 cents stamps=2
cost=500 cents
6s+10t+8e+20w=500
w=2 since two 20 cent stamps wer bought
6s+10t+8e+40=500
minsu 40 both sides
6s+10t+8e=460
divide both sides by 2 to simplify
3s+5t+4e+230
also
10 more 6 cent than 10 cent
s=10+t
8 cent stamps is 3 times 10 cent stamps
e=3t
sub
s=10+t
e=3t
3(10+t)+5t+4(3t)+230
30+3t+5t+12t=230
30+20t=230
minus 30
20t=200
divid 20
t=10
sub back
s=10+t
s=10+10
s=20
e=3t
e=3(10)
e=30
20 six cent
30 eight stamp
10 ten cent
2 twenty cent
