These are just sample answers; there may be other symbolizations that are equally good.  As before, @ stands for the universal quantifier and $ stands for the existential quantifier.
 
1. Intelligent students respect all teachers.
@x(Ix & Sx -> @y(Ty -> Rxy))

2. Teachers respect all intelligent students.
@x(Tx -> @y(Iy & Sy -> Rxy))

3. No teacher respects every student.
~$x(Tx & @y(Sy -> Rxy))
@x(Tx -> ~@y(Sy -> Rxy)
@x(Tx -> $x(Sy & ~Rxy))

4. No student respects an unintelligent teacher.
@x(Sx -> @y(Ty & Rxy -> Iy))
@x(Sx -> @y(Ty & ~Iy -> ~Rxy))

5. Some student does not respect any intelligent teachers.
$x(Sx & @y(Iy & Ty -> ~Rxy))
$x(Sx & ~$y((Iy & Ty) & Rxy))

6. Students who respect all intelligent teachers are themselves intelligent.
@x(Sx & @y(Iy & Ty -> Rxy) -> Ix)

7. Intelligent teachers respect all students, even though not all students are intelligent.
@x(Ix & Tx -> @y(Sy -> Rxy)) & ~@z(Sz -> Iz)
@x(Ix & Tx -> @y(Sy -> Rxy)) & $z(Sz & ~Iz)

note: you don't actually need to use a 'z' here -- the third quantifier could repeat either the x or the y since this variable is not bound by either of the previous two quantifiers.

8. Any student who respects herself respects all teachers.
@x(Sx & Rxx -> @y(Ty -> Rxy))

9. Some student who respects herself respects no teachers.
$x((Sx & Rxx) & ~$y(Ty & Rxy)
$x((Sx & Rxx) & @y(Ty -> ~Rxy))

10. No student who respects all teachers is unintelligent.
@x(Sx & @y(Ty -> Rxy) -> Ix)
~$x((Sx & @y(Ty -> Rxy)) & ~Ix)

11. There is a teacher who does not respect herself unless all students respect her.
$x(Tx & (~Rxx v @y(Sy ->Ryx))
$x(Tx & (~@y(Sy -> Ryx) -> ~Rxx))

12. There is a student who does not respect any student who respects some teacher or other.
$x(Sx & @y(Sy & $z(Tz & Ryz) -> ~Rxy))
 
Note: Here you do need three different variables.