Question

your brother is 1/3 your age. Your sister is 4 years older than your brother. Your sister is 9 years old. Write and solve an equation to find your age 'a'. An equation is _= 9. You are _ years old.

Answer 1

1) Gathering the data:

Brother: 1/3x | 5

Sister: 9 | 9

You : x | 15

Let's firstly fill in the first column. I am 3x yrs old than my bro, that is x yrs old. Or my brother is 1/3 younger than me.

My sister is 9, and as she is 4 yrs older than my brother I can write

Brother's age (x) = 9 -4 yrs

Brother's age = 5

Since I am 3 times older than my brother I am 15 yrs old.

2) Let's try to fill the table:

I ) Equation

Brother's age 1/3x=9-4 ⇒ 1/3x =5

My age is 1/3x =5 ⇒ x= 15

3) The final answer, an equation to find my age:

4 +1/3x =9

1/3x=5

x=15