If x= number of tiles purchased, then at store 1 she will buy x number of tiles for 79 cents per tile and pay 24$ for the saw. At store 2, there is no rental fee if she pays $1.19 per tile for x number of tiles. So you have to write 2 equations, one for each store, and make them equal to each other.
0.79x + 24 = 1.19x
0.4x = 24
x=60 tiles
