Ifind a place that will give me a 20% discount if i spend over $50 . my bill is $75. what is my final bill after the saving

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).

Me with these questions , i don’t understand scientific notation!

What is the distance between (5 - 2i) and (8 + i)?