what is 7x+2/6x+3 - x-1/6x+3 substract the rational expressions Solution Notice that in (7x+2)/(6x+3) - (x-1)/(6x+3), the two rational expressions already have a common denominator, 6x+3. Thus you can subtract the numerator. be careful when distributing the signs. (7x+2)/(6x+3) - (x-1)/(6x+3) = [(7x+2) - (x-1)]/(6x+3) = (7x+2 - x+1)/(6x+3) = (6x+3)/(6x+3) =1.