Answer:
Original amount invested = $3400 .
Step-by-step explanation:
Let the original investment of Steve = $x
Stock increased in the first year = 50% of amount invested
Therefore total amount after one year = x + 0.5x = 1.5x
Commission paid to the stock broker = $350
Amount lost by him = $400
Amount withdrawn by him = $300
Total amount decreased from the amount after 1 year
= 1.5x - (350 + 400 + 300)
= 1.5x - 1050
This remaining amount is doubled, so the final amount
= 2(1.5x - 1050)
= 3x - 2100
This final amount is equal to $8100
3x - 2100 = 8100
3x = 8100 + 2100
3x = 10200
x = $3400
Therefore original amount invested in the stock market was $3400 .