The answer is C
Explaining:
The number of ways 4 digit numbers can be forms using the digits 0 to 9 with no number repeated is given by

The probability that one of the numbers is 9876 is given by
To find the perfect square needed, you take the "middle" value and half it, then square it. so in this case, take -6, half it into 3, and square it to get 9. you'll be adding 9 to both sides
Supplementary angles add to 180
4+5=9
180/9=20
4*20=80
5*20=100
the angles are 80 degrees and 100 degrees