Math
posted by Emily .
This is the question given:
"Peanuts sell for $5/kg and cashews for $20/kg. Mary wants to sell a mixture of peanuts and cashews for $12/kg. How many kilograms of peanuts and cashews would Mary have to mix in order to make 30kg of the $12/kg mixture?"
This is an algebra question and I need to use "proper format" any suggestions?

My suggestion is to solve these two equations in two unknowns:
C + P = 30
5P + 20 C = 12*30 = 360
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Here's how to solve. Multiply first equation by 5.
5P + 5C = 150
Subtract last equation fron second equation.
15C = 210
C = 14 kg
P = 30  14 = 16 kg