Question

Justin is 10 years older than Maggie. Four years ago, Justin was three times as old as Maggie. Find Justin’s age now.

Answer 1

Let Justin's age be x

Let Maggie's age be y

ATQ,

`\pmb {x = 10 + y} \\ \pmb{x-4=3(y-4)}`

Solve using the substitution method!!

• In this way the equation will be easier to solve because we will get the value of both x and y together...

`\pmb{10 + y - 4 = 3(y - 4)}`

`\sf 6 + y = 3y - 12`

`\sf y - 3y =- 12 - 6`

`\sf - 2y =- 18`

`\sf y =9`

Substitute the value of y into the first equation

`\pmb{x= 10 + y} \\ \pmb{x = 10 + 9} \\ \pmb{x = 19}`

Thus, Maggie's age is 9 and Justin's age is 19...~

Answer 2

Note that:

• J = 10 + M
• J - 4 = 3(M - 4)

Finding Maggie's age:

• J - 4 = 3(M - 4)
• => J - 4 = 3M - 12
• => M + 10 - 4 = 3M - 12
• => M + 6 = 3M - 12
• => 12 + 6 = 3M - M
• => 18 = 2M
• => M = 9

Finding Justin's age:

• J = 10 + M
• => J = 10 + 9
• => J = 19