Question

the total sales made by a salesperson was $25,000 after 3 months and $68,000 after 23 months. predict the total sales after 41 months.

Answer 1

You make each into an ordered pair so you will get (3,25,000) and (23,68,000)
So then you will plug it into the slope formula of y2-y1
 68,000-25,000        43,000                                --------
-------------------- =   ----------  = 2150                    x2-x1                                   
         23-3                     20
 now you plug it in 
y=2150x+b
25,000=2150(3)+b
25,000=6450+b
-6,450  -6,450
--------------------
18,550=b
put everything together 
y=2150x+18,550
y=2150(41)+18,550
y=88,150+18,550
y=106,700  dollars for 41 months