COGS : 237
Freight In : 22
Ending Inventory : 147
Gross Purchases : 300
Sales : 400
Purchase Discounts : ?
Beginning Inventory : 150
Gross Profit : 163
Purchase Returns : 50

The formula is:
Beg Inv + Purchases + Frt In - Returns - Disc- Ending Inv = COGS
150+300+22-50-? - 147 = 237
275 - ? = 237
275-237= 38

Apply the following formula:
Beg Inv + Purchases + Frt In - Returns - Disc- End Inv = COGS
Sales - COGS = GP

Apply the following formula:
Beg Inv + Purchases + Frt In - Returns - Disc- End Inv = COGS
Sales - COGS = GP

Apply the following formula:
Beg Inv + Purchases + Frt In - Returns - Disc- End Inv = COGS
Sales - COGS = GP