What does an electric circuit mean?

How can three resistors of resistances $2 \,\Omega$,$3 \,\Omega$,and $6 \,\Omega$ be connected to give a total resistance of $4 \,\Omega$?

Which uses more energy, a $250 \,W$ $TV$ set in $1 \,hr$ or a $1200 \,W$ toaster in $10$ minutes?

$A$ battery of $9 \, V$ is connected in series with resistors of $0.2 \, \Omega$,$0.3 \, \Omega$,$0.4 \, \Omega$,$0.5 \, \Omega$,and $12 \, \Omega$ respectively. How much current (in $A$) would flow through the $12 \, \Omega$ resistor?

An electric heater of resistance $8 \, \Omega$ draws $15 \, A$ from the service mains for $2$ hours. Calculate the rate at which heat is developed in the heater (in $W$).

$A$ hot plate of an electric oven connected to a $220\, V$ line has two resistance coils $A$ and $B$,each of $24\,\Omega$ resistance,which may be used separately,in series,or in parallel. What are the currents in the three cases?