To balance a half-reaction in basic solution, you need to add enough of which substances to balance the equation?

For each of the following types of reactions, write a general reaction formula in the symbolic form—for example, a + b → ab. single-displacement double-displacement synthesis decomposition

Can someone me with questions 15 to 17 plz.

Calculate the ph of a .10m nh4cl solution. the kb value for nh3 is 1.8×10^-5