Mark is alternating sqaure tiles with lengths of 4in and 2 in. along the edge of a 6 foot long wall. If he starts with a 4 in tile and ends with a 2 in tile, how many tiles will he use in all? Draw a diagram to solve.

each combination of small tile and large tile covers 6 inches or 1/2 foot.

So it will take 12 combinations to go 6 feet
That is twelve four inch tiles and twelve two inch tiles just to stretch along the wall.
NOW he needs two more 2 inch tiles for each of the original ones to make the stripe six inches wide.
so he needs
12 of the 6 inch squares
12*3 = 36 of the 2 inch squares

or 12 + 36 = 48 tiles in all

I have ignored the thickness of the grout between the tiles which would really mess this up.