Alex withdraws $40 per month from his average savings account

Only once.

Step-by-step explanation:

Given: Sara goes to the mall every 6th day. Andy goes to the same shopping mall every 7th day.

Then, from starting the first day , the number of day when they meet = L.C.M of (6,7)

Since 7 is a prime number , so the least common multiple of 6 and 7 = 6 x 7 = 42

So, every 42th day they will meet.

Both December and January have 31 days.

Starting from 1st December , they will meet on 11th January because 42 = 31 +11 , where 31 days are of December and next 11 days of January.

next time they will meet 42 days after Also 20 + 22 , where 20 remaining days of January and 22 of February, so next time they will meet on 22nd February.

So, they will meet only once at 11th January in the month of December and January .