Weighted Averages Help

I need some help with averages. If you look at the attachment, P79 & Q80 are averages of the percentages in columns P & Q. They are just an overall average and are not weighted based on the amount of job (column F). Is there any way to base the average percentages on the percentage based on the job amount? I know that probably doesn't make sense but I don't know how else to describe it.