Ok, so:
For Part A, we have: P(Z|A)=P(Z and A)/P(A)
And if we replace, we got:
P(Z|A) = (0.15)/(0.25) and this is equal to 0.6.
For Part B, we have: P(A|Z)=P(Z and A)/P(Z)
P(A|Z) = (0.15)/(0.73) and this is equal to 0.205.
In an equation the Left hand side must equal the right hand side
4(5y-8-2)=185-15
20y-32-8=170
20y=170+32+8
20y=210
Therefore y=10,5
When you substitute the 10,5 and solve it on the left and side it's equal to 170 which is the answer on the right hand side
The answer is 1,000 if you think about 30*1,000=30,000
