word problem

[lmf0610]

Iceburg lettuce is grown and shipped to stores for about 40 cents a head, and consumers purchase it for about 70 cents a head. find the % increase.

I need to know how to set this in an algebra expression...from there i think I can figure it out...% are hard 4 me

 

[Denis]

40 times (what?) = 70
w = what
40w = 70
w = 70/40
w = 1.75
.75 = 75%

So percentage increase = after / before - 1