The function would be y = 0.45x, x being the number of seconds, y being the items he can ring up.
For example (this is an example only to show how this equation works), if we were looking at how many items the cashier can ring in 5 seconds, we would make the equation y = 0.45(5), and with multiplication, we can find that they would ring 2.25 items ( y = 2.25 )
If I misunderstood this question or got something wrong, please leave a comment and I can help further.
