You have three 7 Ω resistors. Using all three each time, find the combined resistance when all are…

Step 1. (a) $7\ \Omega + 7\ \Omega + 7\ \Omega = 21\ \Omega$.

Step 2. (b) $\dfrac{7\ \Omega}{3} = 2.33\ \Omega$.

Step 3. (c) The pair: $3.5\ \Omega$. Plus $7\ \Omega$: $10.5\ \Omega$.

Step 4. (d) The pair in series: $14\ \Omega$. In parallel with $7\ \Omega$: $\dfrac{14\ \Omega \times 7\ \Omega}{21\ \Omega} = 4.67\ \Omega$.