Question

Econ-math question.
"lf we set the absolute value of the MRS(marginal rate of substitution) equal to the price ratio, we have the equation..."
So my mrs is -(y+1)/x+2 and my price ratio is simply one.
From there the instructor wrote (y+1)/(x+2) = 1, which makes sense because absolute value. He then has that => x-y=-1 and that's where I'm confused.