The difference between a number and fifteen is seven. 
Find the number.

22 or 8.

1) Let the number be x
2) x-15 = 7 or 15-x = 7 (Let's slove the first equation first)
3) x-15+15 = 7+15 (add both sides by fifteen)
4) x = 22 (Check: 22-15=7 , 7=7 [it is right])
5) 15-x+x = 7+x (Add x to both sides)
6) 15 = 7+x
7) 15-7 = 7+x-7 (subtract 7 from both sides)
8) x = 8 (Check: 15 = 7+8 , 15=15 [it is right])
9) x = 22 or 8 (FINISH!)


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