A reciprocal of the number or a certain expression is the multiplicative inverse of a certain numbers. This means that the numerator of the original number becomes the denominator of the reciprocal and the denominator of the original number becomes the numerator of the reciprocal.
In this item, the numerator is -8b and the denominator is 5b - 6. The reciprocal of the expression will then be equal to,
R = -(5b - 6) / 8b
