Sandy gets 3 marks for each correct sum and loses 2 marks for each incorrect sum. Sandy attempts 30 sums and obtains 50 marks. How many sums did Sandy get correct?	Choose the correct choice:  A) 20  B) 22  C) 24  D) 26  E) 28

Rationale: "let x be the correct sums and ( 30 - x ) be the incorrect sums . 3 x - 2 ( 30 - x ) = 50 5 x = 110 x = 22 the answer is b ."
Answer: B