9=-(1+7a)+6(1+a)

Solution for 9=-(1+7a)+6(1+a) equation:

Simplifying
9 = -1(1 + 7a) + 6(1 + a)
9 = (1 * -1 + 7a * -1) + 6(1 + a)
9 = (-1 + -7a) + 6(1 + a)
9 = -1 + -7a + (1 * 6 + a * 6)
9 = -1 + -7a + (6 + 6a)

Reorder the terms:
9 = -1 + 6 + -7a + 6a

Combine like terms: -1 + 6 = 5
9 = 5 + -7a + 6a

Combine like terms: -7a + 6a = -1a
9 = 5 + -1a

Solving
9 = 5 + -1a

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.
9 + a = 5 + -1a + a

Combine like terms: -1a + a = 0
9 + a = 5 + 0
9 + a = 5

Add '-9' to each side of the equation.
9 + -9 + a = 5 + -9

Combine like terms: 9 + -9 = 0
0 + a = 5 + -9
a = 5 + -9

Combine like terms: 5 + -9 = -4
a = -4

Simplifying
a = -4