Question: Can you give me some step-by-step instructions for this math problem: A trader buys some bags of wheat from a farmer at a rate of $20 per bag. If it costs $2 to transport each bag from the farm to the warehouse, and the trader made a total profit of $400 after selling all the bags at a rate of $30 each, how many bags did he sell?
Answer: 
Each bag of wheat cost the trader $20+$2=$22 (taking transportation costs into account)
Each bag of wheat was sold for $30 each giving a profit of $30-$22=$8 on each bag
Since a total of $400 profit was made, the total number of bags sold is $400/$8=50 bags