Although each situation is unique because of the circumstances and the deal between investors and the company can be almost what ever both parties agree upon.
Generally, the funds invested purchase equity according to the valuation of the company. In your scenario, if you owned 100 shares of stock in the company (before the transaction) then the company sold 100 shares to an investor - you would each own 100 shares. Assuming no other shares were outstanding- you would each own a 50% interest in the company.
I hope this answers your question. If you want to discuss your specific situation, feel free to drop me a PM or contact me directly.
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