Underoot 60 =
7.75 is the answer to your question!
Notice that the denominators are 3 and 7, which are factors of 21.
So express all the fractions with denominator 21:
On Monday

are sold
On Tuesday

are sold
On Wednesday

are sold
by Thursday

of the tickets was sold.
Answer:
7.6, 8.2, 8.8, 9.4, 10.0, 10.6, 11.2, 11.8, 12.4