Answer: (x-1)(6x-1)
The number is not fully separated so the question might be interpreted in many ways. I will solve this based on assumption that the question is {6(x^2-1)(6x-1)}/{6(x+1)}
{6 (x^2-1) (6x-1)} / {6(x+1)}
{(x^2-1)(6x-1)} / {(x+1)} ------> divide both by 6
{(x-1)(x+1)(6x-1)} / {(x+1)} ------> (x^2-1) = (x-1)(x+1)
{(x-1)(6x-1)} / {1} ------> divide both by (x+1)
Result: (x-1)(6x-1)