Answer:
7 years
Step-by-step explanation:
Total cost = a + (13a/100)
<u>Step-by-step explanation:</u>
Let the price of the monster truck be 'a'
He should pay 13% tax
Total cost = price of the truck + tax
Total cost = a + (13a/100)
The equation to represent the total cost is
Total cost= a + (13a/100)
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
Answer:
a(n) = -20 + 3(n - 1)
Step-by-step explanation:
a(n) = -20 + 3(n - 1)
Answer:
b
Step-by-step explanation:
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