12a-7b-(4a-21b)=

Solution for 12a-7b-(4a-21b)= equation:

Simplifying
12a + -7b + -1(4a + -21b) = 0
12a + -7b + (4a * -1 + -21b * -1) = 0
12a + -7b + (-4a + 21b) = 0

Reorder the terms:
12a + -4a + -7b + 21b = 0

Combine like terms: 12a + -4a = 8a
8a + -7b + 21b = 0

Combine like terms: -7b + 21b = 14b
8a + 14b = 0

Solving
8a + 14b = 0

Solving for variable 'a'.

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

Add '-14b' to each side of the equation.
8a + 14b + -14b = 0 + -14b

Combine like terms: 14b + -14b = 0
8a + 0 = 0 + -14b
8a = 0 + -14b
Remove the zero:
8a = -14b

Divide each side by '8'.
a = -1.75b

Simplifying
a = -1.75b