To find the number of favors Gianna and Moriah can buy, we need to divide the total amount of money they have by the cost of each favor. The cost of each favor is $0.40.
For Gianna:
Gianna has $4.75.
The number of favors Gianna can buy is 4.75 / 0.40 = 11.875.
However, Gianna cannot buy a fraction of a favor, so she can buy 11 favors.
For Moriah:
Moriah has $6.42.
The number of favors Moriah can buy is 6.42 / 0.40 = 16.05.
However, Moriah cannot buy a fraction of a favor, so she can buy 16 favors.
Together, Gianna and Moriah have $4.75 + $6.42 = $11.17.
The total number of favors they can buy is 11 + 16 = 27.
To find the amount of money they have leftover, we need to subtract the cost of the favors they bought from the total amount of money they had.
The cost of 27 favors is 27 * $0.40 = $10.80.
The amount of money they have leftover is $11.17 - $10.80 = $0.37.
Therefore, the answer is 27 favors with $0.37 leftover.