Can I create a sum formula?

Can I create a sum formula?

Good Afternoon,

I'm trying to create the following a pricing formula:

Field A is 100.00
Formula is:
Field A * .50 = Field B
Field A * .60 = Field C
Field A * .25 = Field D

In looking at the formula codes available, I don't see a SUM or anything else that would help me in setting this up.  Appreciate any help.