Asingle-turn circular loop of radius 23 cm is to produce a field at its center that will just cancel the earth’s magnetic field at the equator, which is 0.7 g directed north.

The loop is in the vertical plane and normal to the north direction. The current in the loop can be calculated with the equation : I=2BR, 
where B is the direction (B=0.7G) and R is the radius, 
So,
I=2*7*10^(-5) x 0.1/4pi*1-^(-7) Ampers

Hello how was your day? ? i hope it was good