The following shape has two lines of reflectional symmetry.
$M N O P$ is a square of perimeter 40 cm .
The vertices of rectangle $R S T U$ lie on the edge of square $M N O P$.
$M R$ has length $x \mathrm {~cm}$.
What is the largest possible value of $x$ such that $R S T U$ has area $20 \mathrm {~cm} ^ { 2 }$ ?
..... 7
The following shape has two lines of reflectional symmetry.

$M N O P$ is a square of perimeter 40 cm .

The vertices of rectangle $R S T U$ lie on the edge of square $M N O P$.

$M R$ has length $x \mathrm {~cm}$.

What is the largest possible value of $x$ such that $R S T U$ has area $20 \mathrm {~cm} ^ { 2 }$ ?