Aman spent exactly $2.50 on 3-cent, 6-cent, and 10-cent stamps. if he bought ten 3-cent stamps and twice as many 6-cent stamps as 10-cent stamps, how many 10-cent stamps did he buy?

Yas

t=number of 3 cent
s=number of 6 cent
n=number of ten cent

ten 3 cent stamps (t=10)
and 2 times as many 6 cent as 10 cent (s=2n)
what is n?

find how much are 3 cent
3 times 10=30
30 cents are 3 cents

convert to cents
250-30=220
220=6s+10n
s=2n
220=6(2n)+10n
220=12n+10n
220=22n
divide both sides by 22
10=n

he bought 10 ten cent stamps