Meryll has written 35 questions x 2/5 = <<35*2/5=14>>14 multiple-choice questions.
While she has written 15 questions x 1/3 = <<15*1/3=5>>5 problem-solving questions.
The total number of questions that Meryll has to write is 35 questions + 15 questions = <<35+15=50>>50 questions.
Meryll has written a total of 14 questions + 5 questions = <<14+5=19>>19 questions.
Hence, she needs to write 50 questions - 19 questions = <<50-19=31>>31 questions more.
#### 31