My son is rather algebra-phobic, so to explain concepts requiring variables I usually use a coloured dot or (if no coloured pens are are to hand) a little pictu

My son is rather algebra-phobic, so to explain concepts requiring variables I usually use a coloured dot or (if no coloured pens are are to hand) a little picture. People who grok maths tend to be blind to the confusion that variables can engender, viz if I say "2x = 6" then "x" is to be understood as representing a specific value, which is in contrast to e.g. an area formula like "A = bh", so breaking away from letters altogether is sometimes helpful.