A and B are equally likely.
The chance of A or B happening is .70
The chance of both A and B happening is .40
What is the chance of event A happening?
Just sketched the Venn diagram and thats the only answer I could come up with.
No guarantees it right though
p(a) = p(b)
P(a or b) = 0.7
P(a and b) = 0.4
using the addition rule which is " p (A or B) = p(a) + p(b) - p(a and b)"
let p(a) = x (so P(b) will also = x)
0.7 = x + x - 0.4
1.1 = 2x
x = 0.55