If you find a first you will be able to find b a little faster then it is super easy after that you got this!
Answer:
There was a 1.93% probability of having multiples (twins or more) in 1980.
Step-by-step explanation:
There were 3,612,258 births in the US in 1980.
Of those,
68339 + 1337 = 69676 were multiplies.
So
What was the probability of having multiples (twins or more) in 1980?

There was a 1.93% probability of having multiples (twins or more) in 1980.
<span>We need to calculate noon sun angle. Noon sun angle is an angle at which sun-rays fall at noon on a given date.
</span>On September 22, the sun’s rays form a 90° angle at noon at the equator.
Formula for calculating noon sun angle is:
Noon_sun_angle = 90° - Zenith angle
We have complementary angles so we need to substract zenith angle from 90°.
The zenith angle is the distance between subsolar point (point where sun is at 90°) and the latitude of an observer. In our case this angle will have same value as latitude because subsolar point is at equator 0°. If our latitude and subsolar point are at same hemisphere we substract values. Otherwise we add values.
New Orleans, USA
Latitude = 30°
Noon_sun_angle = 90° - 30° = 60°
Helsinki, Finland
Latitude = 60°
Noon_sun_angle = 90° - 60° = 30°