Sarah is 14
The twins are 12
The youngest (n) is 7
14+(12+12)+7=45
n=7
If it's just distribution, not solving for s (I mean I could but do you need to?):
5(2s² - 3s + 4) Distribute/multiply 5 into (2s² - 3s + 4)
(5)2s² - (5)3s + (5)4
10s² - 15s + 20
26 plus 27 is 53
hope I helped
You would have 640 flies in 3 days.