Answer
a) $b=P-a-c$
b) $c=P-a-b$
Work Step by Step
a) Using the properties of equality, in terms of $
b
,$ the given formula, $
P=a+b+c
,$ is equivalent to
\begin{array}{l}\require{cancel}
P-a-c=b
\\\\
b=P-a-c
.\end{array}
b) Using the properties of equality, in terms of $
c
,$ the given formula, $
P=a+b+c
,$ is equivalent to
\begin{array}{l}\require{cancel}
P-a-b=c
\\\\
c=P-a-b
.\end{array}
