Alright so let's make Jan's age "J" and Trits' age "T"
Jan's age is 3 years less than twice trits age: 2T-3=J
The sum of their ages is 30: J+T=30
We can plug the first equation into the second:
2T-3+T=30
3T-3=30
3T=33
T=11 So Trits' age is 11, and we can plug 11 for T for either equation
2(11)-3=J
19=J
Jan is 19 and Trit is 11 :)