6-7(9+1)=3(2-9)

Solution for 6-7(9+1)=3(2-9) equation:

6-7(9+1)=3(2-9)

We simplify the equation to the form, which is simple to understand 
6-7(9+1)=3(2-9)

Reorder the terms in parentheses
6+(-70)=3*(-7)

Remove unnecessary parentheses
+6-70=+3+*(-7+)

Reorder the terms in parentheses
6-70=+(-21)

Remove unnecessary parentheses
+6-70=-21

We move all terms containing  to the left and all other terms to the right. 
0=-21-6+70

We simplify left and right side of the equation. 
0=+43

0=43

The left and right sides are not equal, therefore there is no solution. This equation is invalid.