The given equation
1p+1q+1x=1p+q+x
⇒1p+1q=1p+q+x−1x
⇒p+qpq=x−(p+q+x)x(p+q+x)
⇒p+qpq=−(p+q)x(p+q+x)
Dividing by p+q on the both sides of the equation:
⇒1pq=−1x(p+q+x)
⇒x(p+q+x)=−pq
⇒x2+px+qx+pq=0
⇒x(x+p)+q(x+p)=0
⇒(x+p)(x+q)=0
therefore
x=−p or x=−q