Answer: Fewer than 8 weeks
Explanation:
1200-620= 580 (States the balance that Millie can use)
580÷72.5= 8 weeks
However, the question asks how many weeks will MIllie's balance remain above $620.
After 8 weeks, her balance will be exactly $620 not above that, so it is fewer than 8 weeks (7 weeks) where Millie's balance will remain above $620.