The probability that one pass is 0.38 or 38%.
What is probability
Independent events are events in probability theory that are not influenced by each other. In other words, the occurrence or non-occurrence of one event does not affect the probability of the occurrence of another event.
Given that the both Tom and Ben take the driving test and probability of passing the test is
P(B pass) = 0.8
P(B fail) = 1-0.8 = 0.2
P(T pass) = 0.7
P(T fail) = 1-0.7 = 0.3
The events are independent so passing the test by only one is
Ben passes x Tommy fail or Ben fails x Tommy passes.
P( 1 pass) = 0.8 * 0.3 + 0.2 * 0.7
= 0.24 + 0.14
0.38 or 38%
Therefore, the probability that one pass is 0.38 or 38%.