my mother is 12 years more than twice my age.after 8 years she will be 20 years less than three times my age...find my age and my mothers age

i have this equation:
2x+12+8=3x-20
2x+12-12+8-8=3x-20-20
2x+3x=-40
5x/5=-40/5
x=-8
NEED HELP PLS :(