Okay.. well did you try to do it on your own at least ? I help you, but what do you know already so we can go on from there.
Point-slope equation=y+1=5(x+2)
slope intercept form=5x+9
15!/(15-9)!= 32432400
i hate these so much hope it helps! :)
The equation you can use is x + 3x = 428 with x as the number of cheeseburgers and 3x the number of hamburgers
you solve for x and get 4x= 428 and x=107
so 321 hamburgers were sold that day.
