Since R is the center of the circle, then the angle ARD has the same measure than the arc AD, which is 120°.
On the other hand, the measure of the arc ABC will be the same as the measure of the angle ARC, which is 180°.
The measure of the arc ADB is the same as the sum of the measures of the angles ARD, DRC and CRB, which is 120°+60°+40°=220°.
Finally, the measure of arc BD is the same as the sum of the angles BRC and CRD, which is 40°+60°=100°.