jmc

Call the difference between two consecutive terms $x$. The third term is then $2+2x$, and the sixth term is $2+5x$. So, $25=(2+2x)+(2+5x)$. Solving for $x$ gives $7x=21$, or $x=3$. So, the fourth term is $2+3\cdot 3=\boxed{11}$.