Observe, and reflect, on what happens when you increase or decrease the value of A or that of B   (with [+] and [-] you can increase or decrease the value of A or B by 1; otherwise you can directly introduce A and B and click [=])

A =   B =   A+B =  

A : %     B : %     A+B : %    A/B = %

  A:
  B:
A+B:

examples