Let required no of pounds of chocolates($1.10 a pound) be x.
∴The no of pounds of chocolates worth 90¢ a pound is (30-x).
∴1.5*x+0.9*(30-x) = 1.1*30 [ ∵Total price of the mixture = $(1.1*30)]
Solving, we get,
∴Required no of chocolates worth $1.50 a pound is 10 pounds.(Ans.)