Answer:
Nailah's is wrong so far. it equals to 5 yards and you need 7-9 yards with 5 pieces of ribbon.
So Nailiah's would be 5 purple's to equal 8.33 Yards which is between 7-9 yards.
add 2 green and 1 blue to Yu's that would equal to 8.66 Yards which is between 7 and 9 yards. Remember that Yu has 3 pieces of ribbon
and for Elena's add 5 blue's and 1 green that would equal to 7.5 yards which is between 7 and 9 yards. remember that Elena has 6 pieces of ribbon