Which of the following expressions will produce an answer with three significant figures? a) 100x3.4 b) 2101/23.7 c) 20 - 40.8 d) 22.67 + 14.6

Significant figures have to do with decimals, so we can already say that A is incorrect since there are none.
B will be: 2101/23.7 = 88.6497... so you can see there are more than three significant figures
C: 20 - 40.8 = 20.8, so this should be the correct answer
D: 22.67 + 14.6 = 37.27, there are 4 significant figures

The correct answer is C. 20 - 40.8