To simplify the expression (3sinx + 6cosx) / (3sinx + cosx), we can first factor out a common factor of 3 from the numerator and denominator:

(3sinx + 6cosx) / (3sinx + cosx)
= 3(sin x + 2cos x) / 3(sin x + cos x)
= (sin x + 2cos x) / (sin x + cos x)

Therefore, the simplified expression is (sin x + 2cos x) / (sin x + cos x).