To calculate the size that the rows should have, perform a decomposition in the prime factors of each number.
For 120 its decomposition is: 5 x 3 x (2 ^ 3)
For 56 its decomposition is: (2 ^ 3) x 7
So we have that the common factor is 2 ^ 3 = 8.
Therefore, the rows must be 8 laymen.
The number of rows for yellow legos is: 7
The number of rows for blacks is: 5 x 3 = 15
In summary, you must make 7 rows of 8 yellow legos and 15 rows of 8 black legos
