Most linear equations have exactly one answer. But sometimes every x cancels out and you are left staring at something like 6 = −5 or 2 = 2. That is not a mistake — it is the answer. Graph each side as its own line and the three outcomes become three pictures you can simply look at.
Each side is a line
LEFT—
RIGHT—
Same slope?—
Same height?—
They meet—
Three possible endingspick a case and step through it
Set a = 2 to make the slopes match, then slide b through 1 and watch the verdict flip from none to infinitely many and back.
The tell. Solve until the x terms are gone or one survives. If an xsurvives, you get exactly one answer. If every x cancels, read what is left: a true statement (2 = 2) means every real number works; a false one (6 = −5) means nothing works.