Stacy is a high school Calculus teacher.  She assigns 45 problems for homework.  There are twice as many multiple choice problems as free response, and 7 more free response than true/false.  How many true/false questions are there?
Let x represent the number of true/false questions.
Free response:x+7.
Multiple choice: 2(x+7)=2x+14.
Total:x+x+7+2x+14=45
4x+21=45
4x=24
x=
<gadget id="calculator">6</gadget>
<output>6</output>
6 true/false questions.

<result>6</result>