A box contains 40 identical discs which are either red or white if probably picking a red disc is 1/4. Calculate the number of; 1. White disc.
2. red disc that should be added such that the probability of picking a red disc will be 1/4

The wording in this question is off... I am assuming you’re asking for the number of white discs and red discs if the probability of picking a red disc is 1/4.
If the probability of picking a red disc is 1/4, there are 10 red discs and 30 white discs.

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4should be the last one n=4