Form calculation field isn't giving correct result

trying to work the equation field. I am stumped on this. 

Thanks for the video explanation, we apperciate it.

The problem was, some of your calculation formula is in string format (brown), switch it to black so they function as a calculation formula.

Here's how:

All the brown should be in black and remove the space (empty brown). The last equal sign is also not necessary.

Let us know if require further assistance.

thank you so much that works.