Here is the code I used in SageMath computations.
var('a11,a12,a21,a22,b1,b2')
A = matrix([[a11,a12,b1],[a21,a22,b2]])
A.add_multiple_of_row(1,0,-a21/a11)
pretty_print(A)
The output is as follows.
Is it possible to simplify the entries in the form a/b?
Thanks for your time.