Elementary arithmetic, with brief notices of its history... by Robert Potts.

11
number, the sum of these partial differences will be the difference of
the two given numbers.
But in cases where a figure of any order in the less number is.
greater than that of the same order in the larger number, the subtraction is not possible.
If this figure be increased by 10 units of the same order, the subtraction becomes possible; and if the figure of the next superior order
in the less number be increased by 1, the larger and smaller numbers
having been equally increased, the difference of the two numbers will.
be unaltered.
Let it be required to find the difference of 456 and 273.
Here 456 consists of 4 hundreds, 5 tens, and 6 units,
and 273 consists of 2 hundreds, 7 tens, and 3 units.
Now 3 units taken from 6 units leaves 3 units, the first partial
remainder.
Next, 7 tens taken from 5 tens is impossible, but 10 tens added to,
5 tens make 15 tens, and the subtraction becomes possible.
Then 7 tens taken from 15 tens leave 8 tens, the second partial
remainder.
But as 10 tens are equal to 1 hundred, 1 hundred added to 2
hundreds make 3 hundreds, and 3 hundreds taken from 4 hundreds
leave 1 hundred, the third partial remainder.
Hence the sum of these partial remainders will be the difference of
the two numbers 456 and 273.
And the difference is 1 hundred, 8 tens, and 3 units, or 183.
The preceding process may be briefly exhibited, and the names of
the orders of the figures may be omitted in performing the operation.
456
273
183 difference.
The number 3 taken from 6 leaves 3. 7 cannot be taken from 5,,
add 10 to 5, which make 15; then 7 taken from 15 leaves 8. Next:
add 1 to 2, which makes 3, and 3 taken from 4 leaves 1; and the dif —
ference of the two nunmbers is 183.
The correctness of the process of subtraction may be readily verified; since of two numbers, the sum of their difference and the less
number is equal to the greater.
6. The operation of the subtraction of one number from another is
denoted by the sign -, called minus. Thus 8- 5 means that 5 is to,
be subtracted from 8, and is read 8 minus 5; also 8 - 5 = 3 is read 8;
minus 5 is equal to 3, or that the difference of 8 and 5 is 3.
When the sum or difference of two or more numbers is required to
be considered as one number, the two numbers connected by the