A made-up box holds 12 phones, and 4 of them are faulty…

Step 1. Both faulty. $\dfrac{4}{12} \times \dfrac{3}{11} = \dfrac{12}{132} = \dfrac{1}{11} \approx 0.0909$.

Step 2. None faulty. $\dfrac{8}{12} \times \dfrac{7}{11} = \dfrac{56}{132} = \dfrac{14}{33} \approx 0.4242$.

Step 3. Exactly one. $1 - \dfrac{1}{11} - \dfrac{14}{33} = \dfrac{16}{33} \approx 0.4848$.