HOW DO I WRITE 1 1/2

You could just write 1.5 it is an equilvilant to 1 1/2

do u mean the sites calculator if so just put 1 1 then the division symbol 2 it should come up a fraction

that works to 

Look here for a general all inclusive answer.

http://web2.0calc.com/questions/how-do-i-type-in-fractions

now 1 1/2 won't work.

you can enter it as  1+1/2    or  (1+1/2)   or   1.5