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Let x be the amount of raisins (in pounds) to be mix.
Then the amount of nuts is (25-x) pounds.
x pounds of raisin cost 14x pesos.
(25-x) pounds of nuts cost 22*(25-x) pesos.
The total cost for ingredients is 14x + 22*(25-x).
Isko wants 25 pounds of the mixture cost 16 pesos per pound. In other words,
= 16 pesos per pound.
It is your basic "money" (or "price") equation.
To solve it, multiply both sides by 25. You will get
14x + 22*(25-x) = 16*25, or
14x + 550 - 22x = 400, or
-8x = 400 - 550 = 150 ====> x = = 18.75.
Answer. Isko should mix 18.75 pounds of raisins with 25-18.75 = 6.25 pounds of nuts.
Check. (18.75*14 + 6.25*22)/25 = 16 pesos per pound. ! Correct !
Solved.