Question

Using the formula P = 2(a + b), find a when P = 15 and b = 5.

Answer 1

\[P=2(a+b)\]
\[15=2(a+5)\]
\[\frac{ 15 }{ 2 }=\frac{ 2(a+5) }{ 2 }\]
\[7.5=a+5\]
\[\frac{ 7.5 }{ -5 }=\frac{ a+5 }{ -5 }\]

Answer 2

\[a=2.5\]