Answer:
The sentence
"The Number of Chem textbooks sold is 86 less than the number of History textbooks"
This seems to be the confusing part.
Now look at it this way...
'If CHM text is 86 less than History text... It also means that History Text is 86 More than CHM'
This expression can be written as
Let History Text be "H"
Let CHM text be "C"
C - 86 = H
or
C=H + 86.......1
First line of this question is interpreted thus
H + C = 326.......2
From eqn 1... C=H+86
Substitute into Eqn 2
H + C=326
H + (H+86)=326
H+H=326-86
2H=240
H=240/2
H=120.
C=H+86
C=120+86
C=206.
This answer is correct... Why?
The key statement says .. The Number of CHM sold is 86 less than History...
Also interpreted as
The Number of CHM – 86 = History
206 - 86 =120.
Have a great day!!!