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Question 573123: Five times the sum of a number and eleven is fifteen.
Answer by mathsmiles(68)   (Show Source):
You can put this solution on YOUR website! Lets use X for the number we're looking for.
5 times the sum ... means we need to figure the sum first and then multiply by 5.
So,
the sum of X and 11 is X + 11
Take 5 times that ...
5 (X + 11)
is 15. Means equals 15.
5 (X + 11) = 15
Multiplying out ...
5X + 55 = 15
Subtracting 55 from each side ...
5X = 15 - 55 = -40
5X = -40
Dividing each side by 5 ...
X = -8
Checking:
5 times the sum of -8 and 11 is 15.
5 times (-8+11) is 15
5 times 3 is 15
15 = 15 Correct!
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