How many of each type of stamp was sold?

[jacywilson14]

A postal clerk sold some fifteen cent stamps and some twenty five cent stamps. Altogether,
10 stamps were sold for a total cost of $1.70. How many of each type of stamp was sold?

 

[skeeter]

Re: another semi hard word problem

let x = number of 15 cent stamps
y = number of 20 cent stamps

Altogether, 10 stamps were sold ...

x + y = 10

... for a total cost of $1.70

(.15)x + (.20)x = 1.70

solve the system of two equations using the methods taught to you in class.