7(a+b)=b-a

Solution for 7(a+b)=b-a equation:

Simplifying
7(a + b) = b + -1a
(a * 7 + b * 7) = b + -1a
(7a + 7b) = b + -1a

Reorder the terms:
7a + 7b = -1a + b

Solving
7a + 7b = -1a + b

Solving for variable 'a'.

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

Add 'a' to each side of the equation.
7a + a + 7b = -1a + a + b

Combine like terms: 7a + a = 8a
8a + 7b = -1a + a + b

Combine like terms: -1a + a = 0
8a + 7b = 0 + b
8a + 7b = b

Add '-7b' to each side of the equation.
8a + 7b + -7b = b + -7b

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

Combine like terms: b + -7b = -6b
8a = -6b

Divide each side by '8'.
a = -0.75b

Simplifying
a = -0.75b