You estimate the product by rounding to the nearest 10:
9 becomes 10 and 54 becomes 50
9 x 50 = 450
In any given week, salesman A earns $65 per sale, so his paycheck amounts to

(where

).
Salesman B earns $40 per sale, with a weekly salary of $300, so in any given week this salesman earns

.
Salesman C earns a flat rate of $900 per week regardless of the number of sales, so his weekly pay is

.
Equation would be: Y = 25 + 5x
Where, x = number of weeks
So, when x = 1, Y = 25 + 5(1) = 25+5 = 30
When x = 2, Y = 25 + 5(2) = 25 + 10 = 35
x = 3, Y = 25 + 5(3) = 25 + 15 = 40
So, Mark the coordinates: (0, 25), (1, 30), (2, 35), (3, 40), (4, 45), (5, 50)...
And draw a line...Graph is done!
Hope this helps!