Explanation:
Given that,
Two resistors of 10 ohms and 15 ohms are connected.
In series combination, the equivalent resistance is given by :
[tex]R_s=R_1+R_2\\\\R_s=10+15\\\\R_s=25\ \Omega[/tex]
In parallel combination, the equivalent resistance is given by :
[tex]\dfrac{1}{R_p}=\dfrac{1}{R_1}+\dfrac{1}{R_2}\\\\\dfrac{1}{R_p}=\dfrac{1}{10}+\dfrac{1}{15}\\\\R_p=6\ \Omega[/tex]
Hence, this is the required solution.