To solve the problem, we need to set up an equation based on the information provided. We know that two-fifths of the total number of residents surveyed (denoted as \( r \)) said they like the beach, and this number equals 80 residents.
We can represent this mathematically as:
\[ \frac{2}{5} r = 80 \]
Now, we can solve for \( r \):
- Multiply both sides by \( 5 \) to eliminate the fraction:
\[ 2r = 80 \times 5 \]
\[ 2r = 400 \]
- Now, divide both sides by \( 2 \):
\[ r = \frac{400}{2} \]
\[ r = 200 \]
Thus, the total number of residents surveyed is \( 200 \).
The correct equation that represents the number of residents surveyed is:
\[ \frac{2}{5} r = 80 \]
And the total number of residents surveyed is \( 200 \).
So the correct option is:
- \( \frac{2}{5} r = 80; \) 200 residents were surveyed.