# What are my chances?

Mark takes both Science and Biology. Past results indicate that the probability of passing Biology is 0.75 and of failing Science is 0.35. The probability of passing at least one of the two subjects is 0.85. The probability that Mark will pass both subjects can be expressed as $$\frac{a}{b}$$, where a and b are positive coprime integers. Find a+b

Notes:

1. This problem is not original
2. Can somebody please post a solution for this
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