We need the bottom half of the fraction to be the same. The closes number we can get for them to be the same is 12. 4x3= 12, and 6x2=12. We multiplied the first fraction's denominator by three, so we do it to the top of that fraction as well. Now the fraction is 3/12. The second fraction we multiples by two and if we do that to the top too, 5x2= 10. Now we have 3/12 and 10/12. 10+3=13 when we add the numerators. Now the fraction is 13/12, or 1 and 1/12. The common denominator is 12
