3. Billy has 20 pencils. Melissa gives Billy some shells.
Billy has 20 pencils. Now Billy has 36 shells. How many shells did Melissa
give him?
melissa give him?

Se tiene en una caja de canicas 10, 4 blancas y 6 negras ¿cual es la probabilidad que en 2 extracciones con reemplazo sean blancas? ¿cual es la probalidad que en 2 extracciones sin reemplazo sean negras?

What is the sum of the first 8 terms of the geometric series

In a small section of a stadium there are 40 spectators watching a game between the cook islands and fiji. they all support at least one of the two teams. 25 spectators support the cook islands and 16 of these support both teams. how many support only fiji?