Write two fractions with different denominators whose LCD is 36.

Two whole numbers whose least common denominator is 36 could be many different pairs: 1 and 36, 2 and 36, 3 and 36, 4 and 36, 4 and 18, 4 and 9, 6 and 36, 9 and 36, 9 and 12, 12 and 36, 12 and 18, 18 and 36, and lastly 36 and 36.

If you want fractions in simplest form, with different denominators, and with an LCD of 36, I would go with 4/5 and 9/13.

I think the reason these work is because 5, 13, and 36 are all pairwise relatively prime (meaning the LCD of any two of them is their product), and because the LCD of 4 and 9 is 36, like I said earlier.