Resposta:
[tex]\textsf{Leia abaixo}[/tex]
Explicação passo a passo:
[tex]\mathsf{p = \dfrac{a + b + c}{2}}[/tex]
[tex]\mathsf{p = \dfrac{12 + 16 + 20}{2}}[/tex]
[tex]\mathsf{p = \dfrac{48}{2}}[/tex]
[tex]\boxed{\boxed{\mathsf{p = 24\:cm}}}\leftarrow\textsf{semiper{\'i}metro}[/tex]
[tex]\mathsf{A = \sqrt{p(p - a)(p - b)(p - c)}}[/tex]
[tex]\mathsf{A = \sqrt{24(24 - 12)(24 - 16)(24 - 20)}}[/tex]
[tex]\mathsf{A = \sqrt{24(12)(8)(4)}}[/tex]
[tex]\mathsf{A = \sqrt{9.216}}[/tex]
[tex]\boxed{\boxed{\mathsf{A = 96\:cm^2}}}\leftarrow\textsf{{\'a}rea}[/tex]
