To find the number of successes x, we need to first find the total number of defective shoes. To do this, we can multiply the total number of shoes selected for quality assurance by the percentage of defective shoes, expressed as a decimal: 386 shoes * 0.0312 = 12.0736. Since we cannot have a fraction of a shoe, we can round down to the nearest whole number to find the number of successes x: 12.0736 rounded down = 12. Therefore, the number of successes x is 12, and the answer is 12.