13+17\dfrac{1}{3} + \dfrac{1}{7}
13+17\dfrac{1}{3} + \dfrac{1}{7}
Since these fractions have different denominators, we need to find the least common multiple of the denominators
The least common multiple of 3 and 7 is 21, so we need to multiply to make each of the denominators = 21
13∗77=721\dfrac{1}{3} * \dfrac{7}{7} = \dfrac{7}{21}
17∗33=321\dfrac{1}{7} * \dfrac{3}{3} = \dfrac{3}{21}
Since these fractions have the same denominator, we can just add the numerators
721+321=1021\dfrac{7}{21} + \dfrac{3}{21} = \dfrac{10}{21}