So one way to answer this would be to write it as a ratio first so you know 4/5 of Chris’s wire = all of Daniels wire so if Chris has 10 ft Daniel has 4/5 of that which is 8 so their ratio is 10:8 which = 5:4. Then Daniel has 1/3 as much as Sarah so we know Sarah has 3x as much so Sarah can be 4x 3 = 12 so your final ratio is 5:4:12 then you have 8 feet of wire and 21 parts total so you do 8/21 and times it by the amount of parts Daniel has which is 4 so 8/21 x 4 is 1.52 ft hope this helps :)