Answer:
20) 8 years
21) Tori could paint the room alone for 3 hours, Sydney could paint the room alone for 5 hours.
Explanation:
A = P ( 1 + r/n ) ^ nt.
8000 = 5000 ( 1 + 6%/4) ^ 4t
8000 = 5000 ( 1 + 0.06/4) ^4t
8000 = 5000 ( 1 + 0.015 ) ^ 4t
8000 = 5000 ( 1.015 ) ^ 4t
8000 / 5000 = ( 4.06 / 4 ) ^ 4t
8/5 = ( 203/200 ) ^ 4t
b = aᶜ ⇔ logₐb = c