20.工地上有水泥a吨,每天用去2.5吨,用了b天后,还剩( )吨.
0 158484 158492 158498 158502 158508 158510 158514 158520 158522 158528 158534 158538 158540 158544 158550 158552 158558 158562 158564 158568 158570 158574 158576 158578 158579 158580 158582 158583 158584 158586 158588 158592 158594 158598 158600 158604 158610 158612 158618 158622 158624 158628 158634 158640 158642 158648 158652 158654 158660 158664 158670 158678 199269
A. | a+2.5b | B. | b+2.5 a | C. | a-2.5b | D. | b-2.5 a |