Watch carefully . . . this could get really tricky:
-20 = -4x -6x
Do you see the -4x and the -6x on the right side ?
I'll bet if it said (4 negative cows) and (6 negative cows), you'd know
right away that you could combine them into (10 negative cows).
-4x - 6x = -10x
So now the equation is -20 = -10x
Multiply each side by -1 : 20 = 10x
Divide each side by 10 : 2 = x
and there you have it.