The system of equations is coincident.

what are the missing values?

4x + 5y = 8
8x + y =

In order the system of equations to be a coincident, determine a number which is a quotient between the two given like terms. The two like terms here are the x variables with different coefficient, that is 4x and 8x.
Divide the two coefficients as 8/4 = 2
The quotient now is 2. You multiply it to the first linear equation on both sides.
2(4x + 5y) = 2(8)

Distributing it yields
8x + 10y = 16

Therefore, the missing values are 10 and 16.