Answer:
<em />
<em />
<em />
Step-by-step explanation:
Given
Shape: Parallelogram PQRS


Required
Find all possible values of x
<em>Every parallelogram have parallel and equal opposite sides;</em>
From the given parameters, one can easily deduce that PQ and SR are opposite sides;
This implies that

Substitute values of PQ and SR

Subtract 3x from both sides


Rearrange

Now, we have a quadratic equation;
Expand the above expression

Factorize


or 
Solve for x in both cases
<em />
<em> or </em>
<em />
<em />
<em>But x can't be negative;</em>
<em>So, the possible value of x is </em>
<em />
<em />