tion:Answer :-For area of remaining cardboard,Area of remaining cardboard = Area of 2 circles + Area of 1 semicircle___________Area of Circle = πr²For Area of 2 Circle = 2πr²Area of 1 semicircle = \sf \frac{1}{2} πr²21πr²Area of 1 semicircle = \sf \frac{πr²}{2}2πr²___________Now,Area of rectangular cupboard = L × bL = R + 2r + 2r = 5rb = 2rArea of rectangular cupboard = L × bArea of rectangular cupboard = ( 5r × 2r )Area of rectangular cupboard = 10 r²___________Now,Area of remaining cardboard = Area of rectangular cupboard - ( Area of 2 circles + Area of 1 semicircle )Area of remaining cardboard = \begin{gathered} \sf 10r² - \bigg( 2πr² + \frac{πr²}{2} \bigg) \\ \end{gathered}10r²−(2πr²+2πr²)Area of remaining cardboard = \begin{gathered} \sf 10r² - \bigg(\frac{4πr² + πr²}{2} \bigg) \\ \end{gathered}10r²−(24πr²+πr²)Area of remaining cardboard = \begin{gathered} \sf 10r² - \frac{5πr²}{2} \\ \end{gathered}10r²−25πr²Area of remaining cardboard = \begin{gathered} \sf \bigg( \frac{20 {r}^{2} - 5 \frac{22}{7} {r}^{2} }{2} \bigg) \\ \end{gathered}(220r2−5722r2)Area of remaining cardboard = \begin{gathered} \sf \cancel2 \bigg( \frac{10 {r}^{2} - 5 \times \frac{11}{7} {r}^{2}}{ \cancel2} \bigg) \\ \end{gathered}2(210r2−5×711r2)Area of remaining cardboard = \begin{gathered} \sf \bigg(10 {r}^{2} - 5 \times \frac{11}{7} {r}^{2} \bigg) \\ \end{gathered}(10r2−5×711r2)Area of remaining cardboard = \begin{gathered} \sf \bigg( \frac{70 {r}^{2} - 55 {r}^{2}}{7} \bigg) \\ \end{gathered}(770r2−55r2)Area of remaining cardboard = \sf \bigg( \frac{15 {r}^{2} }{7} \bigg)(715r2)___________Now, finally Ratio between the area of the remaining cardboard and area of cardboard.Ratio = \begin{gathered} \sf \frac{the \: \: area \: \: of \: \: the \: \: remaining \: \: cardboard}{area \: \: of \: \: cardboard} \\ \end{gathered}areaofcardboardtheareaoftheremainingcardboardRatio = \begin{gathered} \sf \frac{\bigg( \frac{15 {r}^{2} }{7} \bigg)}{10 \: \: r²}\\ \end{gathered}10r²(715r2)Ratio = \begin{gathered} \sf \frac{15 \cancel{ {r}^{2}} }{7 \times 10 \cancel{ {r}^{2} }} \\ \end{gathered}7×10r215r2Ratio = \begin{gathered} \sf \frac{ \cancel5 \times 3}{7 \times \cancel5 \times 2} \\ \end{gathered}7×5×25×3Ratio = \begin{gathered} \sf \frac{3}{14} \\ \end{gathered}143Ratio = \begin{gathered} \large \sf {\UNDERLINE{ 3 : 14 }} \\ \end{gathered}3:14___________I HOPE it HELPS you ❤️✔️I'm sorry I took too LONG time to calculate.congratulations