Answer:

Explanation:
Please find that attachment.
We have been given that in rectangle abcd,
and
. We are also told that m and n are the midpoints of sides ab and bc respectively.
Since m is point of ab, so am and mb will be 4 units each. Similarly, an and nc will be 3 units each.
When we will join a line connecting m and n, it will be hypotenuse of a right triangle mbn.
Now, we will use Pythagoras theorem to solve for mn.




Upon taking square root of both sides, we will get:


Since length cannot be negative, therefore, the length of mn is 5 units.