estimate length of foot, given shoe size and formula

[RossyBoy353]

The length "L" of a man's foot is related to his shoe size "s" by the formula s = 3L - 22. The length is measured in inches. The actual size "s" is rounded to the nearest half unit.

Alan wears a size 8½ shoe. Estimate the length of his foot.

I don't know how I would do this. Can anyone help me?
:roll:

 

[stapel]

Plug the given value for the size in for "s", and solve for the length L.

Eliz.