A hot plate of an electric oven connected to 220 volt coil has 2 resistance coil A and B. Each of 24Ω resistance which may be used separately and parallel. What are the currents in 3 cases?

Voltage (volts) = current (amp) * resistance (Ω)

or
I=V/R (amps)

V=220 volts
Case 1: each resistance alone, R=24Ω
Case 2: in series, R=2*24=48Ω
Case 3: in parallel, R=1/(1/24+1/24)=12Ω

You can then calculate current I in each case using formula above.