Use any two points on the table and the slope formula to find the rate of change:
m = y2 -y1/x2-x1 = (18-12)/(10-5) = 6/5 gallons per minute.
Therefore, the water is going into the tank at a rate of 6/5 gallons per minute or 1.2 gallons per minute.
Use the point-slope formula to write an equation for the line: y-y1 = m(x-x1)
You need to use the slope, and one point from the table.
m = 6/5 I am using the point (0,6) therefore y1=6 and x1=0
y-y1 = m(x-x1)
y-6 = 6/5(x-0)
y-6 = 6/5x
y= 6/5x + 6 This is the equation in slope-intercept form.
We see from the equation (and from the point (0,6)) that the y-intercept is 6. This means that the tank started with 6 gallons of water before being filled with additional water
Hope this helps.