Step-by-step explanation:
There are 2 variables a and c, and there is only 1 equation. Hence we cannot find both variables.
However if we restrict a and c to be positive integers, we will have:
10a + 5.5c = 31
=> 20a + 11c = 62
Since 62 ≡ 2(mod 20) and 11c <= 62,
we have c = 2.
=> 20a + 11(2) = 62, 20a = 40, a = 2.
Therefore a = 2 and c = 2.
Hopefully this explanation helped!
