Verified Answer :

Tanya would be 14 because jassica is 5 and 5x3=15-1=14

We have an equation: 3 (age of Jessica) -1= (age of Tanya)
⇒ 3
5 -1= ?
⇒ ?= 15-1
⇒ ?= 14.

Tanya is 14 years old~