Consider $100x$ votes polled in total.
Then $90x$ were valid & $10x$ were invalid.
Then winner got $\left ( \frac{52}{100} \times 90x \right )$ votes & loser got $\left ( \frac{48}{100} \times 90x \right )$ votes.
It is given that the diffrence of votes b/w winner & loser is $160$,
that is $\left ( \frac{52}{100} \times 90x \right ) - \left ( \frac{48}{100} \times 90x \right ) = 160$
On simplifying this we get
$\left ( \frac{48}{100} \times 90x \right ) = 1920$.
Hence loser got $1920$ votes.