Question

At a school fundraiser, Annie purchases some t-shirts as prizes. The medium sized shirts were $4 per shirt and the large were $5 per shirt. If she ordered a total of 70 shirts with a total cost of $320, how many t – shirts were size medium?

Answer 1

$m+l=70;\;4m+5l=320.$

$l=70-m.$

$4m+5(70-m)=320.$

$4m-5m=320-350.$

$m=30.$

30 t – shirts were size medium.