Janice can type 6 sentences per minute. Today at work, Janice continued working on a paper she started typing yesterday. She typed for 20 minutes, took a break, and typed 15 minutes longer. She then had to erase 40 sentences she had typed incorrectly. After a meeting, she typed for 18 minutes more. In all, the paper had 536 sentences by the end of today. How many sentences did she start with today? Give me reasons, before answering the question
Janice had X sentences from yesterday already typed to start with today. Janice typed 6 * 20 = 120 sentences before her break. She typed 6 * 15 = 90 sentences after her break. She typed 6 * 18 = 108 sentences after her meeting. Therefore, she typed 120 + 90 + 108 = 318 sentences today in all. She had to erase 40 sentences, so she had 318 - 40 = 278 sentences that she typed today left. The paper had X + 278 = 536 sentences at the end of today. Thus, she had X = 536 - 278 = 258 sentences typed on the paper to start with today. So the final answer is 258.