5. Alea is 5 times 3 less than Leo's age. Alea is 40 years old. How old is Leo

• Define a variable

• Write an equation

Solve the equation

Leo is 11 years old

Step-by-step explanation:

* Lets explain how to solve the problem

- Alea is 5 times 3 less than leo's age

- Alea is 40 years old

- Assume that leo's age is x

* Lets change the words to equation

∵ Leo is x years old

∵ Alea is 5 times 3 less than Leo's age

- That means when we subtract 3 from Leo's age and multiply the

difference by 5 the result is Alea's age

∴ Alea's age = 5 (x - 3)

- Multiply the two terms of the bracket by 5

∴ Alea's age = 5x - 15

∵ Alea is 40 years old

- Equate the expression of Alea's age by her age

∴ 5x - 15 = 40 ⇒ the equation to find Leo's age

- Add 15 to both sides

∴ 5x = 55

- Divide both sides by 5

∴ x = 11 ⇒ the solution of the equation

∵ x represents the Leo's age

∵ x = 11

∴ Leo is 11 years old