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.
12-x(5-4k)=y
12-y=x(5-4k)
12-y/(5-4k)=x
10 - 2(7)
10 - 14 = -4
A is the answer
diagonal = sqrt(a^2 +b^2)
20 = sqrt(12^2 +b^2)
20= sqrt(144+b^2)
20^2 = 144 + b^2
400 = 144 + b^2
256 = b^2
b = sqrt(256) = 16
it is 16 inches wide