(-21)=3+b

Solution for (-21)=3+b equation:

Simplifying
(-21) = 3 + b
-21 = 3 + b

Solving
-21 = 3 + b

Solving for variable 'b'.

Move all terms containing b to the left, all other terms to the right.

Add '-1b' to each side of the equation.
-21 + -1b = 3 + b + -1b

Combine like terms: b + -1b = 0
-21 + -1b = 3 + 0
-21 + -1b = 3

Add '21' to each side of the equation.
-21 + 21 + -1b = 3 + 21

Combine like terms: -21 + 21 = 0
0 + -1b = 3 + 21
-1b = 3 + 21

Combine like terms: 3 + 21 = 24
-1b = 24

Divide each side by '-1'.
b = -24

Simplifying
b = -24