First you need to make both denominators the same number.
The number we can use is 21.
6/7 : to make the denominator 21, you need to multiply the numerator and the denominator by 3.
6 × 3 = 18
7 × 3 = 21
The equivalent is 18/21
1/3 : to make the denominator 21, you need to multiply the numerator and the denominator by 7.
1 × 7 = 7
3 × 7 = 21
The equivalent is 7/21
18/21 + 7/21 = 25/21 = 1 4/21
