Answer:
1 4/7
Find a number that will divide evenly into both the top number and the bottom number. (You can do any math operation to either number as long as you do the same to the bottom number.)
Keep doing that until you can't find a number that works.
In this case try 5.
55 ÷ 5 = 11 and 35 ÷ 5 = 7
so: 55/35 = 11/7
since the top number is greater than the bottom, reduce 11/7 to 1 4/7