Let x = to pounds of nuts and y = pounds of raisins
We have two unknowns in the problem therefore we need two equations in order to solve the problem.
Pounds of trail mix = Pounds of nuts + Pounds of raisins
60 = x + y -----> First equation
Cost/lb (lb) = cost of nut/lb (lb) + cost of raisins/lb (lb)
5(60) = 9(x) + 3(y)
300 = 9x + 3y --------> Second equation
Therefore,
x = 20 lb of nuts
y = 40 lb raisins