To find the percentage of the people surveyed who cannot swim, we need to consider both the adults and children who cannot swim.
Let's look at the survey data:
- The proportion of adults who cannot swim is 0.06.
- The proportion of children who cannot swim is 0.12.
We need to sum these proportions to get the total proportion of people who cannot swim.
[tex]\[
0.06 + 0.12 = 0.18
\][/tex]
Next, to convert this proportion into a percentage, we multiply by 100:
[tex]\[
0.18 \times 100 = 18\%
\][/tex]
Thus, the percentage of the people surveyed who cannot swim is [tex]\( 18\% \)[/tex].
The correct answer is [tex]\( \boxed{18\%} \)[/tex].