We have a question: Meryll wants to write 35 multiple-choice questions and 15 problem-solving questions for her Chemistry class. She already has written 2/5 of the multiple-choice and 1/3 of the problem-solving questions. How many more questions does she need to write for both multiple-choice and problem-solving?
And an answer: 31
So how you got the answer?
Meryll has written 35 questions x 2 / 5 = 14 multiple - choice questions. While she has written 15 questions x 1 / 3 = 5 problem - solving questions. The total number of questions that Meryll has to write is 35 questions + 15 questions = 50 questions. Meryll has written a total of 14 questions + 5 questions = 19 questions. Hence, she needs to write 50 questions - 19 questions = 31 questions more.

We have a question: James finds 3 bills in his pocket. They are all 20s. If he already had $75 in his wallet how much money doe he have now?
And an answer: 135
So how you got the answer?
He found 3 * 20 = $60. So now he has 60 + 75 = $135.

We have a question: James paints a 20 ft by 15 ft mural. It takes him 20 minutes to paint 1 square foot and he charges $150 per hour. How much does he charge to paint the mural?
And an answer: 15000
So how you got the answer?
The mural is 20 * 15 = 300 square feet. So it takes him 300 * 20 = 6000 minutes. So he paints it in 6000 / 60 = 100 hours. That means he charges 100 * 150 = $15000.