For the first one bro u r partly correct coz u cannot assume cl stock to be 10000 it can b any amount but the difference betwn cl stock and op stock must come 5000..
Ur Second solution..
First of all we will make debtors a/c to find out our sales figure..since no info regardng cash sales is given so we will assume the credit sales to b only sales made during the year..
So ur credit sales will come to Collections+cl debtors-op debtors..
wich comes to 212000+28000-17000=223000.
Then we can find out the GP wich 25% on sales..
wich comes to 223000*25%=55750.
And our COGS will be 223000-55750=167250
Now, As we knw that COGS=Op stock+Purchases-Cl stock
So, we can write COGS+Cl stock-Op stock=Purchases
We have COGS=167250 and Cl stock-Op stock=5000
So our Purchases will be = 167250+5000=172250