Joe goes camping with his dad on a Friday. Joe's dad has 21 marshmallows, and Joe has four times as much marshmallows as his dad. If Joe’s dad roasts a third of his marshmallows, and Joe roasts half of his marshmallows, how many marshmallows did they roast in total?
Joe's dad roasts 21/3 = 
<gadget id="calculator">21/3</gadget>
<output>7</output>
7 of his marshmallows.
Joe has 21*4 = 
<gadget id="calculator">21*4</gadget>
<output>84</output>
84 marshmallows.
Joe roasts 84/2 = 
<gadget id="calculator">84/2</gadget>
<output>42</output>
42 of his marshmallows.
Joe and his dad roasted 7+42 = 
<gadget id="calculator">7+42</gadget>
<output>49</output>
49 marshmallows in total.

<result>49</result>