Hello!
(a) To find the equation of the line, take the two points and find the slope.
(2, 15), (7, 8)
x1 y1 x2 y2
y2 - y1 / x2 - x1
8 - 15 / 7 - 2
- 7/5
So the slope of the line is -7/5. Now let's plug that in along with one of the points into slope-intercept form.
y - y1 = m(x - x1)
Where 'm' is the slope and (x1, y1) is a point on the line. Let's use the point (7, 8).
y - 8 = -7/5 (x - 7)
Now we can distribute -7/5 into the parenthesis to get it into slope-intercept form:
y - 8 = -7/5x + 9.8)
Now add 8 to both sides:
y = -7/5x + 17.8)
So this is our equation in slope-intercept form.
(b)
How long Anita worked on Day 0 is the same thing as the y-intercept of our equation, 17.8, which means she worked 17.8 hours on Day 0. The value at which her setup time decreased per day is the same as the slope, -7/5, which means it decreased by 7/5 each day.
Hope this Helps! Have A Wonderful Day! :)