The percent of error is the number that they actually happens minus what they expect to do divided by what they expected they were going to do. Then you multiply that number by 100 to get the percent.
7. Mr Jones thinks he’s going to spend 120 by he only spends 94.
94= actual
120= expected
So...
(94-120)/120 x 100
(26/120) x 100
.21666666 x 100
21.6%
22% of error