Which is bigger 1/2 or 9/18

Two ways you can do it:

1. change the first number, so the denominator is the same

1/2 - - > times by 9 (top and bottom) - - > 9/18

which means both numbers are the same value

2. divide them using calculator

1/2 = 0.5

9/18 = 0.5

which again means that both numbers are the same value