Question

cual es el resultado de 7(x-1)-6(x+1)=3x-21

Answer 1

7(x-1)- 6(x+1)=3x-21
7x - 7 -6x - 6 =3x - 21
x - 13 =3x - 21
-13 + 21 =3x - x
8 =2x
4=x

Answer 2

7(x-1)-6(x+1)=3x-21
7x-7-6x-6=3x-21  
despejando 

7x-6x-3x=-21+7+6

sumando

-2x=-8

dividiendo
x=-8/-2

x=4 valor final

comprobando

7(x-1)-6(x+1)=3x-21
7(4-1)-6(4+1)=3(4)-21

28-7-24-6=12-21
-9=-9
solucion correcta x vale 4

7(x-1)- 6(x+1)=3x-21
7x - 7 -6x - 6 =3x - 21
x - 13 =3x - 21
-13 + 21 =3x - x
8 =2x
4=x