Circumference of a circle is C = 2πr.
part 1)
so the radius of the smaller gear is 3 inches, so after a full rotation, namely a revolution, the smaller gear has covered an arc of 2π(3), or 6π.
what angle has the larger gear of 7 inches in radius, has it covered with an arc of 6π?
part 2)
since the larger gear has a radius of 7, in a revolution it will have an arc of 2π(7), or 14π.
now, we know the smaller gear does a 6π arc in a revolution, how many revolutions will it do in an arc of 14π?
part 1)
so the radius of the smaller gear is 3 inches, so after a full rotation, namely a revolution, the smaller gear has covered an arc of 2π(3), or 6π.
what angle has the larger gear of 7 inches in radius, has it covered with an arc of 6π?
part 2)
since the larger gear has a radius of 7, in a revolution it will have an arc of 2π(7), or 14π.
now, we know the smaller gear does a 6π arc in a revolution, how many revolutions will it do in an arc of 14π?