Probability trees. Can someone tell me how im meant to set this one out, and I can work the rest out from there

.8 = P (laura)    

Step-by-step explanation:

Sally passes is .7

both passing is .56

P(sally and laura passing) = P(sally) * P(laura)

                  .56                   = .7 *  P(laura)

Divide each side by .7

.56/.7 =            .7 *  P(laura)/ .7

.8 = P (laura)            

answer: expected value of x = 1.0

step-by-step explanation:

p(x=0) = 0.25

p(x=1) = 0.50

p(x=2) = 0.25

expected value for x = 0×0.25 + 1×0.5 + 2×0.25 = 1.0

relating to or denoting a system of numbers and arithmetic based on the number ten, tenth parts, and powers of ten.

it alot will look like this 4.4