Find the missing side lengths

Two blends of tea are mixed to make a blend that will be sold at the fair. black tea sells for $2.20 per pound and orange pekoe tea sells for $3.00 per pound. how much of each should be used to obtain a 4lb blend selling for $2.50 per pound?

Ineed i been stuck on this question since yesterday

£100.80 divided by 14 equals 7.2 how would we put this as money