Aida starts the week with $18.00. The table below shows the change in the amount of money she has each day.
Day Change in Amount ($)
Monday -5.15
Tuesday +12.40
Wednesday -11.20
Thursday +2.50
Friday x
Aida declares that she ended the week with the same amount of money with which she started the week. Determine the value of x for which Aida's statement is true.
