Can you ask me the question because your file is not showing up for me,
$18.00 if you move the decimal one place to the left 10% tip would be $1.80,
multiply $1.80 x 2 = $3.60 which is 20% for the tip.
$18.00 + $3.60 = $21.60 divide by 4 people = $5.40 per person
What i do know is it that its not c, or d its to high and it is a or b.