Do plants undergo cellular respiration? What organelle do they have that helps you determine the answer?

1. Plants have mitochondria and can perform cellular respiration.

To calculate the average atomic weight, each exact atomic weight is multiplied by its percent abundance, then add the results together and round off to an appropriate number of significant figures.  So according to what's given, the average atomic mass of element M should be (23.9850*0.7899)+(24.9858*0.1000)+(25.9826*0.1101)=24.30