included in your weekly circular should be free coupons, so coupons are free (disregarding the price you have to pay to live around the area)
if you want to know how much discount the coupon give you then
4.5*3/10=1.35
takes off $1.35
proportion method
30/100=x/4.5
3/10=x/4.5
cross multiply or ties both sides by 10*4.5
3*4.5=10x
13.5=10x
divide both sides by 10
1.35=x
discount of $1.35 (coupon saves you $1.35)
