Answer: 2/3
Step-by-step explanation: To add like fractions or fractions that have the same denominator, simply add the numerators and keep the original denominator.
So here, if we add the numerators, we have -1 + 5 which gives us 4 and we put this over our original denominator, 6.
So -1/6 + 5/6 simplifies to 4/6.
Notice however that 4/6 is not in lowest terms so we need to divide the numerator and the denominator by their greatest common factor of 2 to get 2/3 which is written in lowest terms.