Can someone give me some help?

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?

What expression is equivalent to log3(x+4)

Atemperature of 1.64◦f corresponds to answer in units of ◦c.