Power = voltage * Amperage
Solving for amperage yields:
Amperage = Power / Voltage
Power consumed = 2*35 watts = 70 watts
Voltage = 12 to 15 volts
Amperage = 70 / 12 = 6 amps
Amperage = 70 / 15 = 4.7 Amps
Amperage draw will be between 4.7 to 6 amps for two 35 watt lamps