SOLUTION: You guessed the height of the building to be 23 feet, but it was actually 35 feet. Hahahahaha hat was your percent error? Round to the nearest WHOLE percent.
The error was percents = 28.57% = 29% rounded as requested.
The focus in solving such problems is to relate the error to the correct base / (reference) value,
which in this case is 35 ft, the correct height of the building.