15 postcards, 10 envelopes, and a notepad cost------------------- 1.68 dolars
Â
Â
Postcards------------x
Envelopes------------y
Notepad--------------z
Â
15x+10y+z=1.68
Y=z/8Â Â Â Â y=0.02+x
Z=8y     x=y-0.02
15(y-0.02)+10y+8y=1.68
15y-0.30+18y=1.68
33y=1.98Â Â Â y=0.06
Z=8*0.06=0.48
X=0.06-0.02=0.04
Costs
Postcards------------0.04 dolars/ 4 cents
Envelopes------------0.06 dolars/ 6 cents
Notepad--------------0.48 dolars/ 48 cents