The Slope-Intercept form of the equation of a line, is:
Where "m" is the slope of the line and "b" is the y-intercept.
According to the information given in the exercise, you know that The older model submarine can dive down 3 feet per minute. Then, you can identify that:
Let be "y" the location of the submarine (in feet) and "x" the number of minutes.
You can identify that the line passes through this point:
Knowing the slope of the coordinates of a point on the line, you can find "b":
Therefore, knowing "b" and "m", you get that the equation of the line in Slope-Intercept form that models this situation, is: