The nearest whole number to -71.81 is -72, and the nearest whole number to -8.02 is -8
If we divide these two whole numbers we get 9. That's what Martha got.
But actually, the division between those two numbers (with decimals) is 8.953865337.
The error is the difference between the actual value and the calculated value: 9 - 8.953865337 = 0.04613466334 --> this is Martha's error