Given a math word problem, answer the following question. You might need to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the question and then only report the final numerical answer.

there are 45 questions on the math test . 17 questions are word problems . 28 questions are addition and subtraction problems . steve can only answer 38 questions . what 's the difference between the number of all questions on the math test and the number of questions that steve can answer ?
7