What are the two ways of estimating the uncertainty of a measurement?
Either repeat it many times and estimate from the variation you get or look at the process of measurement used, and inspect and test the instruments used.
Uncertainty when adding or subtracting.
Add the absolute uncertainties.
Uncertainty when multiplying or dividing.
Add both of the percentage uncertainties then turn into absolute uncertainty if it asks.
Uncertainty when raising to a power.
Multiply the percentage uncertainty by the power then turn into absolute uncertainty if it asks.