Set he bought x pounds walnuts, then he bought (90-x) pounds pecans.
45*(90-x)+60x=90*55
x=60, 90-x=30.
45*(90-x)+60x=90*55
x=60, 90-x=30.
A Grocer Bought Some Walnuts For 45 Per Pound And Some Pecans For 60 Per Pound. If He Mixed Them For A 90-pound Mixture Worth 55 A Pound, How Many Pounds Of Walnuts Did He Use?