First find the slope m. slope formula:
Let's use (0, -20) for x1 and y1; and (2, 10) for x2 and y2
=
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Now find the y-intercept: the point where the graph crosses the y-axis. The y intercept always has an x value of 0. So -20 is the y-intercept
Use the slope formula
. Slope=m, y-intercept = b
y = 15x - 20
y is the money in the bank account in dollars
x is the day