20x+24=12x-3

20x+24=12x-3        add 3 to both sides

20x + 27 = 12x       subtract 20x from both sides

27 = -8x                 divide both sides by -8

-27 / 8  = x

20x + 24  =  12x - 3

Get all the variables to one side; subtract 12x from both sides:

--->     8x + 24  =  -3

Get all the number terms to the other side; subtract 24 from both sides:

--->     8x  =  -27

Divide both sids by 8:

--->     x  =  -27/8