Multiplying cell

This might be answered somewhere already, but I'm horrible at explaining what I need or looking for, so bear with me as I try to explain this.

I'm trying to set up a sheet that can split up the cost of ordered signs that I made for several different jobs. Basically what I want is that when I input a number in a cell that cell is multiplied by another number, if that makes sense. I have fixed prices for the cost of several signs and I have all the different jobs lined up so I add the quantity the job is using I want it to automatically multiply the quantity with the fixed price, in that cell not a separate cell, but I cant figure it out.  I don't want to create a whole new row to get the product of the quantity and the price.

Any help would be greatly appreciated.