The formula for percentage increase I (given as a decimal) of an investment is I=S−P/P, where P is the purchase price and S is the sale price. You sell a stock at a price of $75, earning a percentage increase of 25%. What was the purchase price of the stock? Also solve the formula for P pls show steps

The temperature of a chemical solution is originally 21 ? c . a chemist heats the solution at a constant rate, and the temperature of the solution 75 ? c after 1212 12 minutes of heating. the temperature, tt t , of the solution in ? c is a function of x , the heating time in minutes. write the function's formula.