-4-21=a

Solution for -4-21=a equation:

Simplifying
-4 + -21 = a

Combine like terms: -4 + -21 = -25
-25 = a

Solving
-25 = a

Solving for variable 'a'.

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

Add '-1a' to each side of the equation.
-25 + -1a = a + -1a

Combine like terms: a + -1a = 0
-25 + -1a = 0

Add '25' to each side of the equation.
-25 + 25 + -1a = 0 + 25

Combine like terms: -25 + 25 = 0
0 + -1a = 0 + 25
-1a = 0 + 25

Combine like terms: 0 + 25 = 25
-1a = 25

Divide each side by '-1'.
a = -25

Simplifying
a = -25