A gambler has won 40% of his 40 poker games for the week so far. If, all of a sudden, his luck changes and he begins winning 70% of the time, how many more games must he play to end up winning 60% of all his games for the week? Answers
A) 50  B) 60  C) 70  D) 80  E) 90

Rationale: "let x be the number of additional games the gambler needs to play . 0.4 ( 40 ) + 0.7 x = 0.6 ( x + 40 ) 0.1 x = 8 x = 80 the answer is d ."
Answer: D