Respuesta :

ColeS1212
The answer would be 60, if you add 13,15, and 12 up you get 40. Those numbers would be considered 2/3 of all the marbles. Divide 40 by 2 to get how many marbles is 1/3. You would get 20 being a third if the marbles. Add that to the original 40 and you’ll get a total of 60.
HamK

Answer: 60

Step-by-step explanation:

Let R be number of red marbels

Let T be Total number of marbels in bag

Now,

T = 13 + 15 + 12 + R

T = 40 + R

Now,

Let P(R) be probability of getting red marble.

P(R) = R / T

1/3 = R / ( 40 + R )

40 + R = 3R

2R = 40

R = 20

So,

T = 40 + R

T = 40 + 20

T = 60