so in this case your denominators are 3 and 4 and they are different denominators so first you have to find the common denominator so in this case it would be twelve so to get that number as the denominator you have in this case multiply the 1 times the three witch would give you three and then the 3 times the 4 witch would give you 12 the denominator witch would be the common denominator for one fraction, but you have another fraction to have same denominator so for the next fraction you would have to multiply the 1 times the four witch would give give you four and then the four times the three witch would give the same denominator witch is twelve so then you would add 3/12 + 4/12