For the funfair, the school organizers ordered 30 rolls of tickets. Each roll of tickets has 100 tickets. The 4th graders bought 30% of the tickets while the 5th graders bought 50% of the remaining tickets. Then the 6th graders bought a total of 100 tickets. How many tickets were left unsold?
There were a total of 30 x 100 = 
<gadget id="calculator">30*100</gadget>
<output>3_000</output>
3000 tickets ordered by the school organizers.
The 4th graders bought 3000 x 30/100 = 
<gadget id="calculator">3000*30/100</gadget>
<output>900</output>
900 tickets.
So, there were 3000 - 900 = 
<gadget id="calculator">3000-900</gadget>
<output>2_100</output>
2100 tickets left for the other two grade levels.
The 5th graders bought 2100 x 50/100 = 
<gadget id="calculator">2100*50/100</gadget>
<output>1_050</output>
1050 tickets.
So, 2100 - 1050 = 
<gadget id="calculator">2100-1050</gadget>
<output>1_050</output>
1050 tickets were left then.
Since 100 tickets were bought by the 6th graders, therefore 1050 - 100 = 
<gadget id="calculator">950</gadget>
<output>950</output>
950 tickets were left unsold.

<result>950</result>