Question: George was selling some of his old toys on the internet. He managed to sell 3 little cars and a set of Legos. In total, he earned $45. How much did the Legos set cost, if one little car was sold for $5? Think carefully first, then make a decision:
George sold 3 cars, so he earned 3 cars * $5 / car = $15 from them. The lego set cost was then $45 - $15 = $30. So the answer is 30.