let

x = the number of new bikes

y = the number of used bikes

A Harley Davidson motorcycle shop maintains an inventory of four times as many new bikes as used bikes:

x = 4y

there are 60 new bikes:

x + y = 60

by solving the system of equations:

x = 4y

x + y = 60

we find:

x = 48 new bikes

y = 12 used bikes

click here to see the step by step solution of the system of equations:

there are 12 used bikes in the shop.