Question

Question #cf87c

Answer 1

Jason is `15`

Explanation:

Let
`color(white)("XXX")J` be Jason's age
`color(white)("XXX")S` be Jason's sister's age
`color(white)("XXX")M` be Jason's mother's age

We are told
[1]`color(white)("XXX")J=S+6`
[2]`color(white)("XXX")M=J+S+15`
[3]`color(white)("XXX")M=39`

Combining [2] and [3], we have
[4]`color(white)("XXX")J+S+15=39`

Using [1], we can substitute `S+6` for `J` in [4]
[5]`color(white)("XXX")S+6+S+15=39`

Simplifying
[6]`color(white)("XXX")2S+21=39`

[7]`color(white)("XXX")2S=18`

[8]`color(white)("XXX")S=9`

Using [8], we can substituting `9` for `S` in [1]
[9]`color(white)("XXX")J=9+6 =15`