Madison buys some five-cent stamps and some ten-cent stamps for a total of $1.00. she receives 13 stamps. how many five-cent stamps does she buy?

Let f= number of five cent stamps
let t=number of ten cent stamps
total spent is 5f+10t=100
total stamps bought is f+t=13

5f+10t=100
f+t=13

f=13-t
5(13-t)+10t=100

65-5t+10t=100
5t=35
t=7
f+t=13
f+7=13
f=6

6 five cent stamps and 7 ten cent stamps