Question 1172688
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You may start from this system of 2 equations in two unknowns


       x +    y = 50      kilograms    (mass equation)

    360x + 400y = 372*50  pesos.       (money equation)


You do the rest.


Or, equivalently, you may start with one single equation


    360x + 400*(50-x) = 372*50         (money equation)


and easily solve it 


    x = {{{(372*50-400*50)/(360-400)}}} = 35.


<U>ANSWER</U>.  35 kilo at 360 pesos per kilo and (50-35) = 15 kilo at 400 pesos per kilo.
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Solved.