The certain number in this word problem is 25.
- Let the certain number be N.
In this exercise, you're required to write a mathematical (algebraic) expression and then use it solve for the unknown variable, which is the certain number N.
Translating the word problem into an algebraic expression, we have;
\(18 + 6N = 168\)
Rearranging the equation (collecting like terms), we have;
\(6N = 168 - 18\\\\6N = 150\\\\N = \frac{150}{6}\)
Certain number, N = 25
Therefore, the certain number is 25.
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