The first thing you should do for this case is write an equation that allows you to find John's sales during the month.
Let
x = amount of money in sales.
The equation is:
4000 + 0.09x = 11650
Clearing x we have:
0.09x = 11650-4000
x = (11650-4000) / (0.09)
x = $ 85,000
answer:
his sales during that month were
$ 85,000
