Researchers safely captured 16 river dolphins and placed a painless tag under their flippers. These river dolphins were quickly returned to the water. Two weeks later, the researchers captured 21 dolphins and found that 3 of them had already been tagged. Estimate the number of river dolphins in the Amazon River. Set the problem up as a proportion with a variable and solve.
(I got this math question and I can't even understand it at all please please help)

Write an equation of the line that passes through the point (2, 3) and is perpendicular to the line x = -1. a) y = 1 b) y = 3 c) y = 0 eliminate d) y = -3

The number of members f(x) in a local swimming club increased by 30% every year over a period of x years. the function below shows the relationship between f(x) and x: f(x) = 10(1.3)xwhich of the following graphs best represents the function? graph of f of x equals 1.3 multiplied by 10 to the power of x graph of exponential function going up from left to right in quadrant 1 through the point 0, 0 and continuing towards infinity graph of f of x equals 10 multiplied by 1.3 to the power of x graph of f of x equals 1.3 to the power of x

How is this equation completed? i cannot find any examples in the book.