The Novolac polymer has mass of 963 g. The number of monomer units present in it are

Monomer unit of Novolac is 

its molecular mass is 124 amu. 

Upon considering molecular weight of polymer as 963 amu (In question its given as 963 gram) Now if during formation of Novolac, (n-1) unit of water are removed then  

$\mathrm{n}\times 124=963+[18\times (\mathrm{n}-1\left)\right]$ 

n=9