Because a triangle's angles need to equal 180, you can subtract 100(30+70) and you will get 80. So 80 will be your third angle.
1250 skiers bought season passes
2500 snowboarders bought season passes
You know a1.
So find a2, a3, and so on until a7.
a(1) = 12
a(2) = 16
a(3) = 20
a(4) = 24
a(5) = 28
a(6) = 32
a(7) = 36
Each is 4 more than the previous.
The answer is 14. The two lower angles are 50 each 100 total and so the top angle must equal 80. If you set it equal to 80 you get 14.
