Find the 14th term of the AP: 2.5, 3.2, 3.9, 4.6, ...

$a=2.5,d=\mathrm{0.7.}{a}_{14}=a+13d=2.5+13\times 0.7=2.5+9.1=11.6$. Watch the traps: 12.3 comes from using 14$d$ instead of 13$d$, 10.9 from using 12$d$, and 9.1 is only the 13$d$ part with the first term left out.