9:2 ; 36:8 ; 54:12 ; 198:44 ; 13518:3004
Because:
[tex]\dfrac{18}{4}=\dfrac{18:2}{4:2}=\boxed{\dfrac{9}{2}}\\\\\\\dfrac{18}{4}=\dfrac{18\cdot2}{4\cdot2}=\boxed{\dfrac{36}{8}}\\\\\\\dfrac{18}{4}=\dfrac{18\cdot3}{4\cdot3}=\boxed{\dfrac{54}{12}}\\\\\\\dfrac{18}{4}=\dfrac{18\cdot11}{4\cdot11}=\boxed{\dfrac{198}{44}}\\\\\\\dfrac{18}{4}=\dfrac{18\cdot751}{4\cdot751}=\boxed{\dfrac{13518}{3004}}[/tex]
