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Define x and y :
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Let the small number be x.
And the big number be y.
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Construct equations :
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The sum of the 2 numbers is 33.
⇒ x + y = 33
The sum of the smaller number and 3 times the larger number is 81.
⇒x + 3y = 81
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Find x and y :
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x + y = 33 ---------------- (1)
x + 3y = 81 .---------------- (2)
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Equation (2) - (1) :
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2y = 48
y = 24
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Sub y = 24 into equation (1) :
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x + y = 33
x + 24 = 33
x = 33 - 24
x = 9
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Find the two numbers :
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Smaller number = 9
Bigger number = 24
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Answer: The two numbers are 9 and 24.
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