A pressure of 15 PSI is equivalent to how many lb/in²?

The correct understanding here is that PSI, which stands for pounds per square inch, is a direct measurement of pressure. Therefore, when the question states that there is a pressure of 15 PSI, this is equivalent to 15 pounds of force applied to each square inch of area. As a result, a pressure of 15 PSI is expressed as 15 lb/in² without any conversion necessary.

It's critical to recognize that PSI is already defined in terms of pounds per square inch, reinforcing that the numerical value given is already in the correct units of measurement for pressure. This makes the answer directly reflective of the relationship between PSI and lb/in².