Question

John is twice as old as Fred. Four years ago, John was 6 times as old. How old is John

Answer 1

Answer: John is 12, Fred is 6.

Explanation:

12/2=6

12-4=8

6-4=2

8/2=4

Answer 2

John: 10

Fred: 5

Explanation:

We can solve this like a system of equations.

Set Variables:

John: j

Fred: f

Given Info:

2f = j

j - 4 = 6(f - 4)

Use the distributive property, a(b+c) = ab+ac to simplify.

j - 4 = 6f - 24

Use info from the first equation and substitute.

j - 4 = 6f - 24

2f = j

6f = 3j

j - 4 = 3j - 24

Add 24 on both sides.

j - 4 + 24 = 3j - 24 + 24

j + 20 = 3j

Subtract j on both sides.

j - j + 20 = 3j - j

20 = 2j

Divide 2 on both sides.

`(20)/(2) = (2j)/(2)`

j = 10

Because j is twice f, divide 10 by 2 to get f.

10/2 = 5