How much of another coffee that costs $1.50 should the cafe mix with the first?

Question

A coffee mix is to be made that sells for $2.50 by mixing 2 types of coffee. The cafe has 40 ml of coffee that costs $3.00. 

Answer 1

(x ml)($1.50) + (40 ml)($3.00) = (40 + x ml)($2.50)

1.50 x + 120 = 100 + 2.5x

x = 20 ml

So, you need 20 mls of the $1.50 coffee mixed with 40 mls of the $3.00 coffee to make 60 mls of $2.50 coffee.