Given‌‌that‌‌a=b,‌‌we‌‌could‌‌say‌‌that‌‌a-b=0‌‌if‌‌you‌‌move‌‌“b”‌‌to‌‌the‌‌other‌‌side.‌‌In‌‌
step‌‌4,‌‌one‌‌has‌‌the‌‌reflex‌‌to‌‌divide‌‌the‌‌equation‌‌by‌‌“(a-b)”‌‌on‌‌both‌‌sides,‌‌but‌‌you‌‌
are‌‌not‌‌able‌‌to‌‌divide‌‌by‌‌0,‌‌and‌‌a=b‌‌meaning‌‌a-b=0,‌‌the‌‌equation‌‌can’t‌‌be‌‌
simplified‌‌in‌‌that‌‌way,‌‌showing‌‌that‌‌a+b‌‌cannot‌‌equal‌‌b.‌ ‌