So to solve for a variable, you just need to isolate the variable onto one side. In this case, isolate a onto one side to solve for it.
7.
Firstly, multiply both sides by a: [tex] au=k [/tex]
Next, divide both sides by u, and your answer will be [tex] a=\frac{k}{u} [/tex]
9.
For this, just divide both sides by 12m, and your answer will be [tex] a=\frac{4}{12m}=\frac{1}{3m} [/tex]
