The perimeter of the isosceles triangle shown is $53 \mathrm{~cm}$. The value of $x$ is
(A) 11
(B) 21
(C) 20
(D) 19
(E) 31

![](https://cdn.mathpix.com/cropped/2024_04_20_6027bc27089ed4fc493cg-039.jpg?height=279&width=295&top_left_y=1666&top_left_x=1316)

$11 \mathrm{~cm}$
The given triangle is isosceles, so the unmarked side also has length $x \mathrm{~cm}$.

The perimeter of the triangle is $53 \mathrm{~cm}$, so $x+x+11=53$ or $2 x+11=53$ or $2 x=53-11=42$, and so $x=\frac{42}{2}=21$.

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