Question

When you add 18 to 1/4 of a number, you get the number it self. where do u get the 3/4 from?

Answer 1

The 3/4 is eighteen.
I'll work it out for you.
4/4 is the number itself. When you subtract 1/4 of it, you get 3/4. 
Hope it helped!

Answer 2

18+(1/4)x=x 
18=x-(1/4)x   

in front of the first x is considered to be 1, so u can write 1/1 but, because u have 1/4 to subtract it's easier to write 4/4 (1/1 and 4/4 are the same) so 4/4-3/4=1/4    :P :))