Question

Pic attached. My answer is n/2, but the back of the book says it's-n/4.

Book is Complete Mathematics for Cambridge IGCSE Extended, Fifth Edition.
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Answer 1

Well to simplify this question, we can have a common denominator. We have to find LCM.
LCM of 4,2,3 is 12

n/4 = n*3/4*3 = 3n/12
m/3 = m*4/3*4 = 4m/12
n/2 = n*6/2*6 = 6n/12

Substituting this is the equation,
(3n - 4m - 6n + 4m)/12

Adding all this up,
-3n/12

Simplifying this,
-n/4

So your answer is -n/4 and the book is right.
Hope it helps you! ;)

Answer 2

Answer:

=n/4-m/3-n/2+m/3

=n/4-n/2(m/3 - m/3 = 0, so we cancelled these two)

=Now take LCM of denominator, I. e. 4 .

= (n-2n) /4

= -n/4