How do you find the amount of 12 dogs decreased by 25%

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?

F(x)=5/6x+3 which of the following is true

Proportions in triangles solve for x