An alloy weighing 30 lbs. is 11% tin. the alloy was made by mixing a 15% tin alloy and a 9% tin alloy. how many pounds of each alloy were used to make the 11% alloy? lbs. of the 15% alloy and lbs. of the 9% alloy.

Amass weighing 16 pounds stretches a spring 8/3 feet. the mass is initially released from rest from a point 2 feet below the equilibrium position, and the subsequent motion takes place in a medium that offers a damping force that is numerically equal to 1/2 the instantaneous velocity. find the equation of motion if the mass is driven by an external force equal to f(t)=cos(2t).