Divide by 21 to put the equation in intercept form.
x/(21/9) + y/(-21/7) = 1
x/(7/3) + y/(-3) = 1
The x-intercept is (7/3, 0)
The y-intercept is (0, -3)
The 3rd choice is appropriate.
The final solutions are C1=7, C2=14
It would be 31. 31 is a whole number. since 0.91 is close to 1. We would round it to 31 because of that.