The probability of having a 17 is the number of ways of having 17 divided by the number of different possible outcomes.
Ways of having 17:
Die 1 Die 2 Die 3 sum
6 6 5 6+6+5 = 17
6 5 6 6+5+6 = 17
5 6 6 5+6+6 = 17
Those are the only 3 possibilities of having 17 (you can only loose 1 point).
The total number of outcomes are 6*6*6 = 216
So the chances (probability) to win is 3 / 216 = 1/72 = 0.0139
point A (-1-1) point B(-2-1)
X+y+5=0
y=-x-5
If a solution exists y=y so we can say
x^2-9x+10=-x-5 add x+5 to both sides
x^2-8x+15=0 now factor
x^2-3x-5x+15=0
x(x-3)-5(x-3)
(x-5)(x-3) so x=3 and 5, using y=-x-5
y(3)=-8 and y(5)=-10
So the two solutions are:
(3,-8) and (5,-10)