I don't see any way of parsing the OP to get: X = X + Y/2 The book costs its cost plus half the price? What? It looks like you're trying to parse it two different ways and combine the result. First you ignore the "plus half its price" bit to say the cost is 1, then you remember the bit you forgot to add half the price anyway. Is that messing about? Or Taching away? Once Tach started on that tack, he consistently had cost=y, price=x The OP says that the book costs $1 plus half of its price. Cost = $1 + Price/2 y = 1 + x/2 Right? Note that adding another equation: x=y then gives the easy answer of $2.