Answer or Solution : The next two rows are 312211, 13112221.

Explanation

It is referred as "Look and say sequence". Each number is formed by looking out the preceding number and reading out its digits. Then forming the next number by grouping the digits written in words.

For Instance,

1 is read as "one one", and so the second number is 11.

11 is read as "two ones", so the third number is 21.

21 is read as "one two, one one", so the fourth number is 1211.

1211 is read as "one one, one two, two ones", so the fifth number is 111221.

111221 is read as "three one, two two, one one", so the sixth number is 312211.

312211 is read as one three, one one, two two, two one, so the seventh number is 13112221.