If the distribution of IQ scores is bell-shaped, with a mean of 100 and a standard deviation of 15,

If the distribution of IQ scores is bell-shaped, with a mean of 100 and a standard deviation of 15, then approximately ____% of IQ scores are less than 55?

A bell-shaped curved implies a normal distribution. By using our empirical rule calculator, we see that:
99.7% of all normal distribution values lie within 3 standard deviations of the mean.

This means the percent of scores less than 55 which is 3 standard deviations away from the mean is:
100% - 99.7% = 0.3%