Some children were riding on the bus. At the bus stop 2 more children got on the bus. Then there were 41 children altogether on the bus. How many children were riding on the bus before the bus stop?
There were $x$ children riding on the bus before the bus stop. 

Then there were $x+2$ children riding on the bus after the bus stop. 

We know that there were $41$ children altogether on the bus. 

So we have the equation:
$$x+x+2=41$$
$$2x+2=41$$
$$2x=39$$
$$x=\frac{39}{2}$$
$$x=19.5$$

There were $19.5$ children riding on the bus before the bus stop.