First of all, thank you very much because you put the brackets just like you had to do !
You can notice that in the solution, there is no more 25 or 50, etc... So we'll simplify by factoring as much as possible
But so :
Simplify by 5 :
Now, you can notice that the red term is very similar to what you want to get : .
This gives you the trick : multiply the denominator & the numerator by
Is it clear enough ?