Urn 1 = 7 red balls and 1 black balls

Urn 2 = 1 red balls and 2 black balls

Urn 3 = 5 red balls and 2 black balls

There are 7+1+5 = 13 red balls.

There are a total of 7+1+5+1+2+2 = 18 balls

P(red) = (number of red balls)/(number of balls total)

P(red) = \(\displaystyle\frac{{13}}{{18}}\)

P(red) = \(\displaystyle{0.722}\)

Urn 2 = 1 red balls and 2 black balls

Urn 3 = 5 red balls and 2 black balls

There are 7+1+5 = 13 red balls.

There are a total of 7+1+5+1+2+2 = 18 balls

P(red) = (number of red balls)/(number of balls total)

P(red) = \(\displaystyle\frac{{13}}{{18}}\)

P(red) = \(\displaystyle{0.722}\)