A jellyfish tank has numerous jellyfish in it. A fifth of the jellyfish are large, and a third of the large jellyfish change color from green to blue under UV light. The other jellyfish are small and always stay blue. When a UV light turned on, 6 jellyfish changed color. How many jellyfish are in the tank?
A third of the large jellyfish change color, so there are 6 * 3 = 
<gadget id="calculator">6*3</gadget>
<output>18</output>
18 large jellyfish.
A fifth of the jellyfish are large, so there are 18 * 5 = 
<gadget id="calculator">18*5</gadget>
<output>90</output>
90 jellyfish in the tank.

<result>90</result>