There's only one number that 'n' can be.
It's called the solution to the equation.
You said n + 4/2 - 3 = 13
Notice that 4/2 is really 2 : n + 2 - 3 = 13
Notice that 2 - 3 = -1 n - 1 = 13
Add 1 to each side: n = 14 .
That's the solution. 'n' is 14 . It's not 28 .