During one day on the stock market, an investor lost $2500 on one stock, but gained $1700 on another. at the end of trading that day, the investors holdings in both stocks were worth $52400. what were they worth when the market opened that day?

[x = Share price] 

52400 = (x - 2500) + (x + 1700) 
We put each share as it will be at the end of the day. 

52400 = 2x - 800 
We expanded/simplified the brackets int eh equation above. 

53200 = 2x 
Over here, we made the -800 on this side of the equation equal 0 so we added 800 to both sides. 

26600 = x 

The answer is 326.78.