Our least common denominator possible is 10. The fraction 3/10 already has a 10 as a denominator, so we just need to change the 2/5 to a fraction with a denominator of 10. Hmm, how can we do this? Well, we can multiply 5 by 2 to get 10!! Don't forget to multiply 2 to the denominator as well as the numerator. (2 * 2)/(5 * 2) = 4/10
So, our pair of fractions would be 3/10 and 4/10.
Hope this helps!! Let me know if you have ANY questions.