There are $25$ superheroes in total. After subtracting $6$, there are $25-6=19$ left. 
In the Avengers League, there are $25$ superheroes. Six of the superheroes from the galaxy guard left. How many heroes are left?~(adapted from $$2007$$ Math kangaroo Problems, Level $$1-2$$, Question \#$$6$$) 

[a] $$19$$ 
[b] $$23$$ 
[c] $$24$$ 
[d] $$25$$ 
[e] $$20$$ 