The simple interest formula is
[tex]I=\text{Prt}[/tex]where I is the interest, P the principal, r the interest rate and t the time.
In this case, we have P=13710, r=0.03 and t=3 years.
By substituying these values into the above formula, we have
[tex]I=(13710)(0.03)(3)[/tex]hence,
[tex]I=1233.9[/tex]Therefore, Tessa will save 1233.9 dollars in 3 years.