Secure Bunker

Enigma:

a = ? a+1 = 4((a÷2)−(12,5×4)÷2)−(59÷10)^2

b = ? b+1 = a+1 +((b1+b2+b3+b4)÷5)-1

c = ? c+1 = b

Spoiler: Solution

a+1 = 2111

b+1 = 2112

c+1 = 1324

I think it's not very fair to rate this level because I saw the numbers in the spoiler... but the funny thing is that although I'm not good with math I'm not a total disaster either, but still I don't know how to get to those results with those equations ... liked the design

ex: a is the base number indicated on the face and a+1 is the number to put
b1 is the first number of b, b2 the second...

@delator77
I fixed it, try again if you want
it's me who didn't pay enough attention to what I wrote