Question

The sum of three times a number and 15 is 42.Find the number

Answer 1

Given : The sum of three times a number and 15 is 42.

To Find : What is the number?

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❍ Let us assume, that the number is 'x'. According to the question,

• The sum of three times a number and 15 is 42.

$\sf{ \therefore \: 3x + 15 = 42}$

$\sf{ \mapsto \: 3x = 42 - 15}$

$\sf{ \mapsto \: x = \dfrac{ \cancel{27}^{ \: 9} }{ \cancel{3}_{ \: 1} }}$

$\purple{\sf{ \mapsto \: x = 9}}$

Therefore, the number is 9.

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Verification :

$\bf{ \longmapsto \: 3x + 15 = 42}$

❐ Substituting x = 9, we get

$\sf{ \longmapsto \: 3(9) + 15 = 42}$

$\sf{ \longmapsto \: 27 + 15 = 42}$

$\sf{ \longmapsto \: 42 = 42}$

$\red{\sf{ \longmapsto \: LHS = RHS}}$

$\bf{Hence, verified. \: \checkmark }$