The point of the Compute(" ") command was that there was actually three terms in the original code block that had to be calculated. Plus for those question marks to work as default +/- signs the variable has to be a math object. But I did try your "random" designation of the variable just to experiment. Unfortunately the questions marks no longer work as default +/- signs.
But now it appears that if I just use "+" signs instead that the correct sign does display for each term.
Those Question marks were borrowed from some older code blocks and it seems now they are not necessary.
Sorry for all the trouble!