A poll is taken from a large enough population that the confidence intervals are governed by a normal distribution, and one candidate is favored at 54%, with a standard deviation of the poll at 4% (so 68% probability the result will fall between 50% and 58% in favor of the candidate).
how would you find out how many people were polled?
The standard deviation of a sample proportion is given by
$$s=\sqrt{\frac{\hat{p}(1-\hat{p})}{n}}$$
We know $\hat{p}=0.54$ and we're given that $s=0.04$
Now we have an equation with one unknown.