I haven't touched algebra in years, so bear with me.
The start of the equation is..
(plus or minus) +/-.76 = x/0.0200-x
the two it splits into are..
x= 0.0200 X 0.76 / 1.76 = 0.0086
x= -0.0200 X 0.76 / 0.24 = -0.063
I understand you're solving for both positive and negative numbers, but without intermediate steps I'm not sure how the first part jumps to the next two equations.
Help would be very appreciated. Thanks.