1.
He could add and subtract, but hadn't learned to divide.
他会做加减法，但还没有学会除法。
2.
The little girl has begun to learn to add and subtract.
这小女孩已在学做加减法了。
3.
Lucy knows how to add and substract but fractions have her up a stump.
做加减法，露西不成问题，可分数却难倒了她。
4.
The little boy can add, subtract and multiply, but cannot divide.
那小男孩会做加法、减法和乘法，但不会做除法。
5.
Students who cannot even do simple addition and subtraction.
学生甚至不会做简单的加法和减法。
6.
Addition and subtraction we call the first- progression operation, multiplication and division we call the second– progression operation.
加法和减法叫做第一级运算,乘法和除法叫做第二级运算.
7.
an advantage bestowed by legislation that reduces a tax on some preferred activity.
通过立法来减税的做法。
8.
The danger students who can not even do simple addition and subtraction.
危险的地方还在于，学生们可能甚至不能做简单的加减法。
9.
Harm Reduction approach
减低毒品危害的做法
10.
attempts to reduce soil erosion
减少土壤侵蚀的做法
11.
Suppose that you receive the calculator for testing and find that besides addition, subtraction, multiplication, and division, it also performs square roots.
假如您收到的测试用计算器除了能加法，减法，乘法，除法以外还能做平方根运算。
12.
addition by subtraction
采用减法运算的加法
13.
Try adding up this time instead of subtracting.
这次试用加法，不用减法。
14.
Please add up this time instead of subtracting.
这次请用加法，不用减法。
15.
In order to relieve the working pressure of traffic police, we should carry on the division and subtraction of depressurization through adjusting the group and individual sentiments.
缓解交警的压力,要通过调节群体和个体情绪,做好降压的除法、减法和加法。
16.
In offices there are slide rules for multiplication and division, and desk machines which can add, subtract, multiply and divide.
在办公室里有能做乘法除法的计算尺，以及能加减乘除的台式计算机。
17.
We may also record our notes on tapes so as to often listen to them easier, to deepen our impression and to lighten our burden of memory.
更胜一畴的做法是把笔记录成音,这样我们可以经常听一听来加深印象和减轻记忆负担.
18.
When we do subtraction,we take things away.
当我们做减法的时候，我们取走事物。