Question

Hi I have a maths problem I can't figure out please someone help.

Zac had some 2c stamps and 5c stamps.he needed to put 30c on a postcard to mail it.what combinations of stamps could he use.

Answer 1

Assuming we can pay using either all 2c or 5c stamps...
let's start with
0 2c ----> 6 5c
1 2c ----> leaves 28 c, can't be done with 5c's
..
5 2c ---> leaves 20 c, paid with 4 5c
..
10 2c ---> 2 5c
15 2c ---> 0 5c

so in the form (2c , 5c) we have
(0,6) , (5,4), (10,2), and (15,0)