Question 1189337
the slope intercept form of the equation of a straight line is y = mx + b.
m is the slope
b is the y-intercept.


in this problem, y represents the total cost and x represents+ the number of hours.


the formula becom3es y = 35 * x + b


when y = 840 and x = 20, the formula becomes 840 = 35 * 20 + b
simplify to get 840 = 700 + b
solve for b to get b = 140.


the additional cost of the material can be assumed to be part of the up front cost which is the 140 dollars.
that's the initial value.


the rate of change is 35 dollars.
that the cost per hour.


if the painters take 20 hours to finish the job, then the total cost is 840 because 20 * 35 + 140 = 840.