X: -2| -1| 0| 1| 2|
y: 1.25| 2.5| 5| 10| 20|
A: 1:1 unless they want you to count both arms then it would be B: 2:2

One really simple way to find an equivalent fraction is just to multiply the numerator and denominator.
For example, for the first answer,
, I simply multiplied the numerator and denominator each by 2. This gives you an equivalent fraction.
You can then continue with this process using numbers such as 3, 4, 5, and 6 as your multiplication factor.
3/5 is greater because the decimal is .6 while 21/40 is .525