GMAT Quantitative Reasoning Practice Test 4

Indicate A as the probability of Michael passing the driving test.
The probability of Sam passing the test is $\frac{1}{4}$, the probability of both events happening together is $1∕6$ so:
$\frac{1}{4}\times \mathit{A}=\frac{1}{6}$ therefore $\mathit{A}=\frac{2}{3}$.