Answer:
30 tiles need to buy for same cost in both store.
Explanation:
Let x be the number of tiles to buy for same cost in both store.
18+0.69 · n = 1.29 · n,
1.29n -0.69n =18 or
0.6n =18
n =18/0.6=30
Therefore, 30 tiles need to buy for same cost in both store.[Ans]