let Tritt's age = t & Jan's age = 2t - 3
if the sum of their ages equals 30 then..
[tex]t + 2t - 3 = 30[/tex]
combine terms and simplify
[tex]3t = 27[/tex]
now simply divide
[tex]t = 9[/tex]
and to find Jan's age just plug 9 in
[tex]2(9) - 3[/tex]
[tex]18 - 3 = 15[/tex]
Jan's age = 15
Tritt's age = 9