a. 86.5-0.07
The result of the subtraction is:
[tex]\begin{gathered} 86.50 \\ -0.07 \\ ----- \\ 86.43 \end{gathered}[/tex]As the answer should have only three significant figures then, the result is: 86.4
b. 30.61-87.3-42.109
The subtraction is:
[tex]\begin{gathered} 30.61 \\ -87.30 \\ ----- \\ -56.690 \\ -42.109 \\ ------ \\ -98.799 \end{gathered}[/tex]As the answer should have only 3 significant figures, then the result is -98.8
