Let [tex]k=[/tex] Kevin's age
Let [tex]d=[/tex] Daniel's age
We know
[tex]k=3d[/tex]
and
[tex]k-4=5(d-4)[/tex]
Plug the value of [tex]k[/tex] into the second equation:
[tex]3d-4=5(d-4)[/tex]
[tex]\rightarrow3d-4=5d-20[/tex]
[tex]\rightarrow-2d-4=-20[/tex]
[tex]\rightarrow-2d=-16[/tex]
[tex]\rightarrow d=8[/tex]
So Daniel is 8 years old.
