Final answer:
To find the number of tiles Margo must buy for the cost to be the same at both stores, set up an equation using the costs of tiles and renting a tile saw from each store. Solve the equation to find the value of x.
Step-by-step explanation:
To determine how many tiles Margo must buy for the cost to be the same at both stores, we need to set up an equation based on the costs of purchasing tiles and renting a tile saw from each store. Let's denote the number of tiles as x.
At the first store, the cost of tiles would be 0.99x and the cost of renting a tile saw would be $18.
At the second store, the cost of tiles would be 1.19x and there would be no cost for renting a tile saw.
Setting up an equation: 0.99x + 18 = 1.19x
By solving this equation, we can find the value of x, which represents the number of tiles Margo must buy for the cost to be the same at both stores.