Resistance in series will be given as R = 10+10 → 20

Resistance in parallel will be given as \(\frac{1}{R}\) = \(\frac{1}{10}\) + \(\frac{1}{10}\) 

\(\frac{1}{R}\) = \(\frac{2}{10}\) → \(\frac{1}{R}\) = \(\frac{1}{5}\)

Resistance in parallel = 5

Total resistance = 20 + 5 → 25ohms