Answer:
a set of two or more equations, each containing two or more variables whose values can simultaneously satisfy both or all the equations in the set, the number of variables being equal to or less than the number of equations in the set.
Step-by-step explanation:
It works because of two properties of equations: Multiplying (or dividing) the expression on each side by the same number does not alter the equation. Adding two equations produces another valid equation: e.g. 2x = x + 10 (x = 10) and x − 3 = 7 (x also = 10).
Answer:
0.0286 or 2.86%
Step-by-step explanation:
The total number of people that have werewolfism is 21,000.
Of those 21,000, 600 also have vampirism, while the remaining 20,400 do not. Therefore, the probability that someone has vampirism, given that they have werewolfism is:

The probability is 0.0286 or 2.86%.
Slope = (y2 - y1)/(x2 - x1)
slope = (7 - -2)/(-3 - 6)
slope = 9/-9
slope = -1