Need to know if my answer are correct or no ?

[Martingale]

so

P(A) + P(B) - P(A B) = P(A). P(B)

0.5 + P(B) - 0.8 = 0.5 P(B)

P(B) - 0.3 = 0.5 P(B)

P(B) = 0.5/0.3 _{(Is this correct?)}

How can P(B) = 0.5/0.3? That number is greater than 1!!

from my work can u please point out the mistake

start from here...
P(B) - 0.3 = 0.5 P(B)

and solve for P(B) again.

[zorro]

start from here...
P(B) - 0.3 = 0.5 P(B)

and solve for P(B) again.

P(B) - 0.3 = 0.5 P(B)

P(B) - 0.5 P(B) = 0.3

P(B) [ 1 - 0.5 ] = 0.3

P(B) 0.5 = 0.3

P(B) = 0.3 / 0.5 _{(Is this correct ?)}

[Martingale]

start from here...
P(B) - 0.3 = 0.5 P(B)

and solve for P(B) again.

P(B) - 0.3 = 0.5 P(B)

P(B) - 0.5 P(B) = 0.3

P(B) [ 1 - 0.5 ] = 0.3

P(B) 0.5 = 0.3

P(B) = 0.3 / 0.5 _{(Is this correct ?)}

Yes