Divide the numerator and denominator by the greatest common divisor (GCD), which is 10 in this case. This gives 11/36 as the answer.
20/360 = 1/18 in its simplest form
140/360 is equivalent to 7/18 in simplest form.
90/11
10/13
13/60
1/4
2/3
1/2
360/2880 = 1/8
42/360 = 7/60
8/360 = 1/45
3/10