Well, whenever you are working with fractions with different denominators, you would multiply both the top and the bottom of the fraction with the smaller number as the denominator. (You could also divide the larger denominator number.) So let's see what number we can multiply by 5 to get 10. That would be 2. Then we would multiply the numerator by two as well. So what is 3 times 2? 6. Once you've done that, you get 6/10 or 0.6 in decimal form. The difference would be 0.3 or 3/10. :)