Jack wants to send thank you cards to everyone who got him a gift for his wedding.  He sent out 200 invitations.  90% of people RSVPed but only 80% of people who RSVPed actually showed up.  Then 10 people who showed up didn't get a gift.  How many thank you cards does he need?
He got 200*.9=
<gadget id="calculator">200*.9</gadget>
<output>180</output>
180 RSVP.
Of those only 180*.8=
<gadget id="calculator">180*.8</gadget>
<output>144</output>
144 people showed up.
So only 144-10=
<gadget id="calculator">144-10</gadget>
<output>134</output>
134 got him gifts and hence need thank you cards.

<result>134</result>