I bought $30.00 of Bitcoin. The price at that time was $6,896.00. The price now is $8,074.00. How much did I make? And how do I do the math?
You have not made any money until you have sold your bitcoin. The numbers in the previous answer refer to your unrealised capital gains. Remember that you may have to pay tax on your gains if you do decide to sell and adjust your winnings accordingly.
30 / 6896 * 8074 = 35.1247099767981
So, you've made a net profit of $5.12., which is (5.12 / 30) a profit margin of 17.06 percent.
For a more indepth answers about realized and unrealized profit/loss for investments, and specifically Bitcoin, check What happens if I buy Bitcoins and the price goes down?