Question 373108
There are two numbers whose sum is 72. One number is twice the other. What are the numbers? 
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Let x = first number
then from "One number is twice the other." we have
2x = second number
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From: "There are two numbers whose sum is 72" we derive our equation:
x + 2x = 72
3x = 72
x = 24 (first number)
Second number:
2x = 2(24) = 48
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Also. There are three consecutive integers. the sum of the smallest and largest is 36. 
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Let x = first consecutive integer
then
x+1 = second consecutive integer
x+2 = third
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From:"the sum of the smallest and largest is 36" we get:
x + x+2 = 36
2x+2 = 36
2x = 34
x = 17 (first)
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Second:
x+1 = 17+1 = 18
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Third:
x+2 = 17+2 = 19