In that case, be careful when operating a division or subtraction: As you can see in the following flow chart, there is one arrow and one simple line. They indicate the order of the mathematical operation. 

The solution would be ...

... because 6 - 4 = 2 (6 - 2 = 4 is also possible).

The arrow always points to the solution of the calculation. The number indicated by an arrow must be subtracted from the other number. 

This also applies to the division (see next page).