SOLUTION
It is given that the sum of the base and is 12
It follows:
[tex]\begin{gathered} x+h=12 \\ h=12-x \end{gathered}[/tex]
The area of the triangle is:
[tex]A=\frac{1}{2}xh[/tex]
Substitute h=12-x into the equation
[tex]\begin{gathered} A=\frac{1}{2}x(x-12) \\ A=\frac{1}{2}x^2-6x \end{gathered}[/tex]
