(a) The element boron is in column (or group) 13 of the periodic table and has a valency of 3. So all the elements in the same column of peridic table as boron will have valency of 3.
(b) The element fluorine is in column (or group) 17 of the periodic table and has a valency of 1. So all the elements in the same column of periodic table as fluorine will have a valency of 1.