3 + (-5) + 8 + (-4)

= 2 +8+(-4)

=2+4

=6mn i.e. the answer....

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As all of them are having the same variables, we can see that they are having the same values.

But some of them are positive, while the others are negative so weea d the positive variables together first.

3mn+8mn=11mn

Now, we add the negative variables together.

(-5mn)+(-4mn)=-9mn

now we subtract 9mn from 11mn.

11mn-9mn=2mn

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