To convert a ratio to a percentage you take the first number in the ratio, divide it by the second number, and then multiply by 100, appending a percent sign at the end.

Example: 3:1 as a percent would be 3/1 = 3 then 3 x 100 = 300. So the ratio would be 300%. Now for the 1:2 ratio you would take 1 and divide it by 2, which would give you 0.5. now you multiply 0.5 by 100 to get the percent, which is 50%