Let's use a for number of days when he shot 50 shots and b for number of days when he shot 100 shots.
We have:
a + b = 20
We also know that he shot total of 1250 shots:
50a + 100 b = 1250
We have two equations. We can solve them for a and b. Let's rearange first equation for a:
a= 20 - b
We insert this into second equation:
50 * (20 - b ) + 100b = 1250
1000 - 50b + 100b = 1250
50b = 250
b = 5
a = 20 - 5
a = 15
Mark shot 100 shots on 5 days.

Plug in what we know:

Find the cube root of both sides:
![\sf~a=\sqrt[3]{2744}](https://tex.z-dn.net/?f=%5Csf~a%3D%5Csqrt%5B3%5D%7B2744%7D)
Simplify:
Looks like you've got 3 lines that are all parallel with one transversal diagonally running down the middle.
Since all of the other lines are parallel to one another, there are only two different angle combinations to be made by the transversal and one of the other lines, one of which being the given 60º angle.
The other one is found by subtracting that from 180 since a straight angle measures 180º.
180 - 60 = 120
The smaller ones are always 60º, and the larger ones are always 120º.
That means that a = 60, b = 60, and d = 60
It also means that c = 120 and e = 120.
Hope this helps!
It is 9lt-2w-27! Hope it helped!