Answer: B
Explanation: if you look at A and try to combine like terms, you will add the -x on the right side the the one on the left, cancelling out the x on the left. then you have 0=x+0, and unless x=0, it is not true.
With B, when you add x to the -x, you cancel it out, giving you 0=0, which is true. hope it helps!
3 slots
1st slot has 10 possible people
2nd slot has 9 possible people (1 less than previous)
3rd slot has 8 possible people
so there are 10*9*8 ways or 720 ways
I think that the best answer here would be that A = 40 degrees.
