She died and left behind a husband, three sons and six daughters

Praise be to Allah.

If a woman dies and leaves behind three sons and six daughters, and her husband and father died before her, then the entire estate goes to her children, with each male getting the share of two females. If the estate is 150,000 riyals, then the share of each daughter is 12,500 riyals and the share of each son is 25,000 riyals. 

If what you mean is that she died and left behind the children mentioned and also left behind a husband, and it is only the parents who are deceased, then the estate is to be divided as follows: 

The husband gets one quarter, because there are descendants who inherit. 

The rest goes to the children, with each male getting the share of two females. 

So the husband's share of the estate is 37,500 riyals. 

The share of each daughter is 9,375 riyals.

The share of each son is 18,750 riyals. 

And Allah knows best.