Energy/power is not gained or lost going through a (ideal) transformer.
So the transformer in this problem really doesn't matter. If the lamp is using energy at the rate of 60 watts, then the whole contraption is getting 60 watts of power from the wall outlet.
Power = (voltage) x (current)
60 watts = (120 v) x (current)
Current = (60 watts) / (120 v)
Current = 0.5 Ampere
