Work hours calculating start and end times

Okay, this should probably be an easy answer but I seem to be having a brain block.
Example =(F142-G142)*24
my start time is 10am and end time is 3pm I know my hours worked aren't 7 it is 5 what am I missing?

What is in F142 and G142?

I have made a userform that returns a time value into the cells and those cells are formatted to the time value the reason for F142 and G142 is that is just where I happened to be when I thought that I would try to create this formula. Do you think it is the way it was set up in the userform? My first intention was to do the calculations within the form but I am a newbie to VBA, that would make seasoned users cringe by the sight of my codes :/ and when I do it the other way as Jeff has suggested I get a negative number. I have attached my workbook if that helps I was just trying to create the formula on the excel employee timesheet tab.

Please ignore the blue writing at the top of it when opening, I had asked a different question then decided to try a different direction which is where this question came.

Thank you for your help guys, I figured it out, just have to make sure the AM and PM is listed in the userform. Maybe I should use military time instead =) Thanks again!