How do you solve the equation

3 (1+x) = -3 (x+1)

x=-1

simplify: 3 (x+1) = -3 (x+1)

3x+3=-3x-3

minus 3 from each side to cancel out the - 3:

3x=-3x-6

add 3x to each side to cancel out the - 3x:

6x=-6

single out the x by dividing 6 from both sides:

x=-1