To find out how many surfboards Sunny's Surf Shop sold last week, we can set up a simple equation based on the information given.
Let \( x \) be the number of surfboards sold last week. According to the problem, 320 percent of \( x \) is equal to 160 surfboards sold this week. We can express this mathematically as:
\[ \frac{320}{100} \times x = 160 \]
This simplifies to:
\[ 3.2x = 160 \]
Next, we can solve for \( x \) by dividing both sides by 3.2:
\[ x = \frac{160}{3.2} = 50 \]
Therefore, Sunny's Surf Shop sold 50 surfboards last week.
So, the answer is 50.