There's only information to answer question C.
We can only know that 32 marbles were chosen. (yellow and black)
Why?
To answer the first two questions (a and b), we need to know the total number of marbles, so, we can only answer the last question (c).
We know that 7/10 of the 20 yellow marbles were chosen.
So, calculating we have:

Also, we know that 18 black marbles were chosen, so, the total of marbles chosen is equal to 32 (yellow marbles and black marbles)

Have a nice day!
Answer:
Yes, it is effectively infinite
Step-by-step explanation:
An effectively infinite population refers to population from which it is possible to obtain a computable sub-population from it, and it is also effectively possible to construct another new sub-population from that same population that will not have elements already contained in the first sub-population.
The attributes of this kind of population is called effective infinity.
Database of recent graduates of any university possess this kind of attributes since it is possible to obtain another over 30,000 recent graduates from the database that will not have elements of the first 30,000.
Is this Spanish, because I don't really know Spanish.
Answer:
It/p= r
Step-by-step explanation:
divide p and t out of the r and multiply by the recipricol