A+b=z and z+b =a then b=?.........what is b

B is 0

B = z - a
B = a - z

z - a = a - z
2z = 2a
z = a. (numbers are equivalent)

Therefore, since a number minus the same number is zero, a - z is 0 and z - a is 0

Therefore, B is 0

From first equation a+b = z
From second equation z+b = a or z= a-b
Now a+b = z and a-b = z
therefore (a+b)-(a-b) = z-z = 0
or, a +b -a +b = 0
or, 2b = 0
or, b=0

So the answer is b=0

a + b = z (equation 1)
z + b = a (equation 2)

substitute equation 2 to 1

(z + b) + b = z
b + b = z - z
2b = 0
therefore b = 0

b = z - a
b = a - z

z - a = a - z
2z = 2a
z = a

b = 0