Answer:
The unknown number is 2.
Step-by-step explanation:
Let x represent the unknown number.
It is multiplied by 9 then added to 3. Hence, it can be represented by the expression:
[tex]9x + 3[/tex]
The sum is equal to the product of 3 and 7, or 21. Therefore:
[tex]9x + 3 = 21[/tex]
Solve for x. Subtract 3 from both sides:
[tex]9x = 18[/tex]
And divide both sides by 2. Hence:
[tex]x = 2[/tex]
In conclusion, the unknown number is 2.
