Given, f is the greatest integer and g is the absolute value function

Now, gof(7/5) = g(f(7/5))

                       = g(f(1.4))   

                       = g(1)               {since f is a greatest integer, So f(1.4) = 1}

                       = 1

Again, fog(-7/5) = f(g(-7/5))

                          = f(g(-1.4))

                          = f(1.4)                  {since g is a absolute value function, So g(-1.4) = 1.4}

                          = 1                        {since f is a greatest integer, So f(1.4) = 1}

Now, gof(7/5) - fog(-7/5) = 1 - 1

=> gof(7/5) - fog(-7/5) = 0