it just means to distribute the negative through the parentheses.
4/5x - x -1/2 = 1/10x + 1/10
combine like terms on the left -1/5x - 1/2 = 1/10x + 1/10
subtract 1/10x from both sides -3/10x - 1/2 = 1/10
add 1/2 to both sides -3/10x = 6/10
multiply both sides by -10/3 and x= -2