Answer:
10 carpenters can make 15 chairs in that amount of time.
Step-by-step explanation:
One carpenter can make 18 chairs / 12 carpenters = 1.5 chairs in a certain time (assuming a constant rate of chair making per carpenter).
Therefore, 10 carpenters can make 10 carpenters * 1.5 chairs/carpenter = 15 chairs in the same time.