To solve the problem, we can set up a proportion based on the information given.
We know:
- For every 3 stocks that went up, there are 4 stocks that went down.
- This gives us a ratio of stocks that went up to stocks that went down as \( \frac{3}{4} \).
Let \( x \) be the number of stocks that went up. According to the problem, we know that 424 stocks went down, so we can set up the proportion:
\[ \frac{x}{424} = \frac{3}{4} \]
Now we cross-multiply to solve for \( x \):
\[ 4x = 3 \times 424 \]
Calculating the right side:
\[ 4x = 1272 \]
Now, divide both sides by 4:
\[ x = \frac{1272}{4} = 318 \]
Thus, the number of stocks that went up is \( \boxed{318} \).