Consecutive numbers are numbers that follow one right after the other. One example is the set {6, 7, 8}. We don't know the three consecutive numbers so let's define...
x = first number
x+1 = second number
x+2 = third number
where x, x+1, and x+2 are consecutive numbers
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"The sum of three consecutive numbers is -15" meaning that
x+(x+1)+(x+2) = -15
Let's solve for x
x+(x+1)+(x+2) = -15
x+x+1+x+2 = -15
3x+3 = -15
3x+3-3 = -15-3
3x = -18
3x/3 = -18/3
x = -6
So this means
first number = x = -6
second number = x+1 = -6+1 = -5
third number = x+2 = 6+2 = -4
The list of consecutive values is {-6, -5, -4}
They add up to (-6) + (-5) + (-4) = -11+(-4) = -15
which confirms we have the right values
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In short, the final answer is -4
