Answer:
31/15
Explanation:
First, find the common multiplier of 20 and 12 (the lowest number that both fractions can be increased to). This is 60 (12 x 5 = 60, 20 x 3 = 60) and adjust the numerators accordingly: multiply 17 by five to get 85, and multiply 13 by three to get 39. Add them up to get 124/60, and then simplify - the answer will be 31/15! Hope this helps! Sorry if this was tough to understand, typing off my phone, so feel free to ask any questions :)