P(not 3)=5/6 this is the correct answer
Based on the calculations, the unknown number is equal to 
- Let the unknown number be x.
<h3>How to find an
unknown number:</h3>
Translate the word problem into an algebraic expression, we have;
Adding 21 to the unknown number:

Multiplying the result by 3:

84 more than two-thirds of the unknown number:

Equating the equations, we have:

Cross-multiplying, we have:

Read more on word problems here: brainly.com/question/13170908
X=12*(21/14)=18 // you can find the ratio of the according sides.
-》D
X=625
His savings is 25% of his monthly budget
25% of 2500 is 625