Rita is adding 3 + (negative 8) + 1. She rewrites the expression as 3 + (negative 1) + 8. What is Rita’s error? She used the commutative property, which cannot be used with negative numbers. In the new expression, –8 and 1 should both be negative. She used the associative property which should only be used with positive numbers.. She switched the negative signs for –8 and 1.