A parallelogram of it's two adjacent side is 3 and 7 find length of it's small diagonal?

Question

AB-3 and BC-7 then AC-?

Answer 1

First, you should learn that IT'S only can mean "IT IS"--IN YOUR PROBLEM, THE POSSESSIVE (ITS) is required.

 

There can be many parallelograms having two consecutive sides of lengths 3 and 7. The particular parallelogram is determined by a particular angle at their intersection.

 

Because of this variability, your question cannot be answered.