we have the following:
[tex]\begin{gathered} A=\frac{b\cdot h}{2} \\ b=x+2 \\ h=x \\ A=20 \end{gathered}[/tex]replacing:
[tex]\begin{gathered} 20=\frac{(x+2)\cdot x}{2} \\ 20\cdot2=x^2+2x \\ x^2+2x-40=0 \\ x=5.4;x=-7.4 \end{gathered}[/tex]therefore, the answer is:
x = 5.4
base (x+2) = 7.4
height = 5.4
[tex]\begin{gathered} A=\frac{7.4\cdot5.4}{2} \\ A=20 \end{gathered}[/tex]