Dear Nayanika,
The answer seems correct to me. If the total amount purchased is 100, the first statement provides enough information to solve the problem, because there's no other possible solution (2 items - $20; 3 items - $30).Thus, the second statement only gives additional but unnecessary information.
XXXX,
RCMV
Correction: The only possible is (2-$20; 2-$30)...sorry!!!!!
[]'s
Rcmv