The guy who links files is pretty annoying amiright...
Divide 18/35 by 3/5 to get your answer. You can also multiply 3/5 by 35/18.
5 goes into 35 7 times, so cross out the 5 and 35 and put 1 and 7. 3 goes into 18 6 times, so cross out the 3 and 18 and put 1 and 6.
Now you have 1/1 times 7/6. Your answer is 7/6.