4. 计算下面各图形的面积。(单位：$cm$)

(4.5+12.5)×3.85÷2=32.725(cm²)
3.6×2.8÷2=5.04(cm²)

5. 解方程。
$x÷2.8 = 4.48$ $2(x + 3.6) = 12.4$ $8x + 6x = 4.2$
$8(x - 9) = 64$ $11x÷6 = 5.5$ $x - 0.05x = 20.9$

$​ \begin{aligned}$解：$x÷2.8×2.8&=4.48×2.8 \\ x&=12.544 \\ \end{aligned}​$
$​ \begin{aligned}$解：$2(x+3.6)÷2&=12.4÷2 \\ x+3.6&=6.2 \\ x+3.6-3.6&=6.2-3.6 \\ x&=2.6 \\ \end{aligned}​$
$​ \begin{aligned}$解：$14x&=4.2 \\ 14x÷14&=4.2÷14 \\ x&=0.3 \\ \end{aligned}​$
$ \begin{aligned}​ $解：$8(x-9)÷8&=64÷8 \\ x-9&=8 \\ x-9+9&=8+9 \\ x&=17 \\ \end{aligned}$
​
$​ \begin{aligned}$解：$11x÷6×6&=5.5×6 \\ 11x&=33 \\ 11x÷11&=33÷11 \\ x&=3 \\ \end{aligned}​$
$​ \begin{aligned}$解$:0.95x&=20.9 \\ 0.95x÷0.95&=20.9÷0.95 \\ x&=22 \\ \end{aligned}​$