Answer:
36 days
Step-by-step explanation:
Zaynnah checks her bike every 9 days for repairs and Amna checks her bike every 12 days.
Now, multiples of 9 are 9, 18, 27, 36, 45, ......
And the multiples of 12 are 12, 24, 36, 48, 60, ........
So, the smallest multiple which is common for 9 and 12 is 36.
Therefore, after 36 days they both check their bikes for repair.
If they both check their bikes today, then after 36 days they will check their bikes on the same day. (Answer)
