If liam arranges chairs in 9 rows of the same length, he has 3 chairs left over. if he arranges the chairs in 7 rows of that same length, he has 19 left over. how many chairs does liam have?

Let x represent the number of chairs in a row and y total number of chairs that Liam has.

We write system:

9*x + 3 = y
7*x + 19 = y

9*x + 3 = 7*x + 19
2x = 16
x = 8   That means that row's length is equivalent of 8 placed chairs.

Liam has:
7*8+19 = 56 + 19 = 75 chairs.