Nine hundred tickets were sold to a concert. Three-fourths of those who bought the ticket came before the start of the concert. Five-ninths of the remaining came few minutes after the first song. Eighty people arrived during the middle part of the concert while the rest did not go. How many of those who bought the tickets did not go?
900 x 3/4 = 
<gadget id="calculator">900*3/4</gadget>
<output>675</output>
675 people came before the start of the concert.
900 - 675 = 
<gadget id="calculator">900-675</gadget>
<output>225</output>
225 people did not come before the start of the concert.
225 x 5/9 = 
<gadget id="calculator">225*5/9</gadget>
<output>125</output>
125 people came few minutes after the first song.
So, 125 + 80 = 
<gadget id="calculator">125+80</gadget>
<output>205</output>
205 people came to the concert that was not able to be at the start of the concert.
Therefore, 225 - 205 = 
<gadget id="calculator">225-205</gadget>
<output>20</output>
20 people did not go to the concert.

<result>20</result>