Looks like your if statement is checking a list the contains a list. Change it to if x in i[1]:
and it should be all fine. Here is my code that works.
a = range(20,30)
b = range(1000,5000)
list1 = [["range a", a],["range b", b]]
x = int(input())
for i in list1:
if x in i[1]:
print (i[0])
Tested it in a IDLE with Python 3.7.0 and here is my direct output.
>>> a = range(20,30)
>>> b = range(1000,5000)
>>> list1 = [["range a", a],["range b", b]]
>>> x = int(input())
25
>>> for i in list1:
if x in i[1]:
print(i[0])
range a
If it still don't work for you maybe you have a problem in your IDE.