I think it's the whole "you bought it again ..." that's tripping some people up. Just ignore that part. Nobody cares if it was the same cow, a different cow, or something else entirely. Money in minus money out!
You bought something for 800, sold it for 1000. 200 profit. You bought something (doesn't matter at all if it's the same cow, another cow, or a damn stripper pole) for 1100, sold it for 1300. Again a profit of 200. 200+200=400.
You spent a total of 1900, received a total of 2300. Profit = 400.
You put in $800 for the cow and sell it for $1000. To buy it back you have to spend that entire $1000 plus an additional $100, so you've invested $900 of your own money overall.
(Or if they mean for tax purposes, there are two taxable events: one where sell the cow for $200 profit, and another where you sell it for another $200, so $400 total in taxable gains.)
Comments
1000 - 800 = 200
200 + 1000 = 1200
1200 - 1100 = 100
100 + 1300 = 1400
You made 400$
Buying it at 1100 loses you 100 in an asset leaving you with 100 in profit
Selling it at 1300 nets you 200, plus 100, equals 300 in profit
You spent a total of 1900, received a total of 2300. Profit = 400.
you spent: 800 + 1100 = 1900
you sold for: 1000 + 1300 = 2300
what you are left with = 2300 - 1900 = 400
(think of it this way - you had $1900 and you bought 2 cows and then sold them for $2300)
You put in $800 for the cow and sell it for $1000. To buy it back you have to spend that entire $1000 plus an additional $100, so you've invested $900 of your own money overall.
Then you sell it for $1300.
$1300 - $900 = $400