-4(25-21)=a

Solution for -4(25-21)=a equation:

Simplifying
-4(25 + -21) = a

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

Multiply -4 * 4
-16 = a

Solving
-16 = 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.
-16 + -1a = a + -1a

Combine like terms: a + -1a = 0
-16 + -1a = 0

Add '16' to each side of the equation.
-16 + 16 + -1a = 0 + 16

Combine like terms: -16 + 16 = 0
0 + -1a = 0 + 16
-1a = 0 + 16

Combine like terms: 0 + 16 = 16
-1a = 16

Divide each side by '-1'.
a = -16

Simplifying
a = -16