Michael’s age is three more than twice Ashleigh‘s age. The sum of their age is 18. If M represents Michael‘s age and a represents Ashley‘s age, which system of equation represents the statements above?

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).