To get from relative error to absolute error, you can use the formula:
Absolute error = Relative error x Value
In your case, you have calculated the relative error as 0.18. To find the absolute error, you need to multiply this value by the corresponding value from your problem, which is 1.08 g/mL.
Absolute error = 0.18 x 1.08 g/mL = 0.1944 g/mL
Now you have the absolute error, which represents the uncertainty in your measurement. This means that the actual value could range from 1.08 - 0.1944 = 0.8856 g/mL to 1.08 + 0.1944 = 1.2744 g/mL.
So your final result, taking into account the uncertainty, is 1.08 +/- 0.1944 g/mL. You can simplify this as 1.08 +/- 0.19 g/mL (significant figures rounding).
Note: Absolute error is usually expressed with the same number of significant figures as the measurement itself.