ANSWER
The correct choice is A.
EXPLANATION
If the the two prisms are similar, then their corresponding sides are in the same proportion;
This implies that
![(x)/(20) = (6)/(3)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/3uso9ab6pb2we0yshxn2osyq8zpmh86bpp.png)
We simplify to get;
![(x)/(20)=2](https://img.qammunity.org/2020/formulas/mathematics/middle-school/qqt2isct6a7jh6ff1mt6n79s1s03mf62yg.png)
We now multiply both sides by 20 yo obtain;
![(x)/(20) * 20 = 2 * 20](https://img.qammunity.org/2020/formulas/mathematics/middle-school/czejecc78sx1lseeyaxw7fc1b58qoe3c1k.png)
We simplify and multiply out to get:
![x = 40](https://img.qammunity.org/2020/formulas/mathematics/middle-school/35o9zwymbyrxdf6x774crvp1yzxm1h09oq.png)
Therefore the value of x is 40 units