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!
90 and 91...................
X - the number
the quotient of the number and 8 = x/8
10 more than the quotient of the number and 8 = (x/8)+10
10 more than the quotient of the number and 8 is at least 12 = (x/8)+10≥12
Given:
ratio of stickers to erasers: 3 to 8
She has 12 stickers.
3:8 = 12:x
3x = 8*12
3x = 96
x = 96/3
x = 32 erasers.
Mrs. Robbins has 32 erasers.
Answer:
The answer is r < 4
Step-by-step explanation:
Isolate the variable by dividing each side by factors that don't contain the variable.
hoped this helped!
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