Final answer:
The unknown number is 5.
Step-by-step explanation:
In this problem, we are asked to define a variable, write and solve an equation, and provide an answer in a sentence.
a. Define a variable:
Let's define the variable 'x' as the unknown number.
b. Write and solve an equation:
Six times the sum of a number and 3 is equal to 12 less than 12 times the number.
6(x + 3) = 12x - 12
Distribute on the left side: 6x + 18 = 12x - 12
Subtract 6x from both sides: 18 = 6x - 12
Add 12 to both sides: 30 = 6x
Divide both sides by 6: x = 5
c. Answer in a sentence:
The unknown number is 5.