I think it would take 24 hours or 10 hours
explanation: if you have 4 hours from Erin, and 6 hours from Cathy, it’ll most likely be 10 hours because you’re trying to find out the total amount. (keyword: together & how many)
56*365=20440
56/4=14 (this is how many leap years are within 56 years)
20440+14=20454 days
Substract 6 to both sides and you get 36 =-2d then you use the multiplicative inverse and d=-18.