( 95 ) 
Thus it appears, that Subtraction differs 
from Addition only in reverfing the figns 
of the fubtrahend. 
This i all very true. Thefe are the rules 
which you- will find in the elementary books 
of Algebra. But this confounding Sub- 
traction with Addition, ferves only to jum- 
ble the ideas of the learner. The following 
general rule is fuffident both for Addition 
and Subtraction. 
In Addition, when the Jlgm are the fame, 
ADD; when they are oppojlte> SUBTRACT. In 
Subtraction, when the figns are the fame, SUB- 
TRACT; when oppojite, ADD. This rule be- 
ing obferved, you proceed naturally, with- 
out any fuppofed change of figns. The 
reafons for the three firft parts of this Rule 
are felf-evident : the laft requires explana- 
tion. I have faid, that, in Subtraction, when 
the figns are oppofite, that is, when one is 
+ and the other , you are to add the co- 
efficients. How, you will afk, will this ad- 
dition be in reality a fubtraction. I will firft 
prove the fact, and then account for it. 
From iotf 56 To loa 56 
Take 56 Add +56 
loa ' loa 
In 
