Answer:
[tex]\$17,500[/tex]
Step-by-step explanation:
Let
x----> that month's sales
y----> October earnings
we know that
[tex]8\%=8/100=0.08[/tex]
[tex]y=0.08x+1,400[/tex] -----> equation A
[tex]y=2,800[/tex] -----> equation B
Equate equation A and equation B and solve for x
[tex]2,800=0.08x+1,400[/tex]
[tex]0.08x=2,800-1,400[/tex]
[tex]x=1,400/0.08[/tex]
[tex]x=\$17,500[/tex]