I am not sure maybe it is 6
When they say quotient, they want a fraction, so the answer for that would be

and the decimal form of that would be 0.6. You can get that from dividing 6 by 10 and solving with long division.
5x + 4y = 24
Substitute y for 1
5x + 4 = 24
5x =20
x = 4


hope this helps!
p.s. can i have brainliest?
5.21 would just be 5 or 5.2 depending on what place you need to round.