Question 778485
salary 800

let sales =x


commission = 9% on sales above 1200

=0.09*(x-1200)


Then I = 800+0.09*(x-1200)

1800=800+0.09x-108

1000-800+108=0.09x

308=0.09x
308/0.09=x

x=3422

He will have to make sales of 3422+800=$4222.22