the absolute error is:
actual - estimate = 33.2 - 35 = -2.8
that in percent can be found using a rule of three, we say that 33.2 is the 100%, and we find the % for 2.8
33.2 ml -------> 100%
2.8 ml -------> x
x =(2.8)(100)/33.2
x = 8.4
then the percent error is 8.4%