Bob spent 25% more time on his research project than he had planned. He had spent an extra h hours on the project. What expression could represent the number of hours Bob actually spent on the project

Let the projected number of work hours be w.

Then the number of hours he actually worked was 1.25w. This represents the number of hours that Bob actually spent on the project.

Another way in which to answer this would be as follows:

Actual work hours = w + h (h hours beyond the projected w work hours).

This w + h is equivalent to 1.25w. This means that h = 0.25w.