360^o makes a circle, earths single rotation takes 24 hours, 360^o divided by 24 hours gives 15^o. So in 1 hour, the earth covers 15^o. Therefore 45^o equals 3 hours. In time calculation when you move eastern you gain (addition). The question says noon. SO we move eastwards and gain 15^o = 1 hour, 45^o = 3 hours, being noon. We gain so three hours place noon equals 3 pm