Take the top line for example, notice the 'difference' between the number that goes in and the number that comes out, i.e. 5 <> 1 = 4, 7 <> 3 = 4, 2 <> -2 = 4.....the answer is always '4' so input '4' then move down a line and do the same until you input the code and press 'Enter'
Take the top line for example, notice the 'difference' between the number that goes in and the number that comes out, i.e. 5 <> 1 = 4, 7 <> 3 = 4, 2 <> -2 = 4.....the answer is always '4' so input '4' then move down a line and do the same until you input the code and press 'Enter'