a) 111222 = 111.1000 + 111.2 = 111.1002 = 111.3.334 = 333.334
b) \begin{align}
& \underbrace{111...1}_{n}.\underbrace{222...2}_{n}=\underbrace{111...1}_{n}.1\underbrace{000...0}_{n}+\underbrace{111...1}_{n}.2=\underbrace{111...1}_{n}.1\underbrace{000...0}_{n-1}2 \\
& =\underbrace{111...1}_{n}.3.\underbrace{333...3}_{n-1}4=\underbrace{333...3}_{n-1}3.\underbrace{333...3}_{n-1}4 \\
\end{align}
c) 444222 = 222.2.1000 + 222 = 222.2001 = 222.3.667 = 666.667
d) \begin{align}
& \underbrace{444...4}_{n}.\underbrace{222...2}_{n}=\underbrace{222...2}_{n}.2.1\underbrace{000...0}_{n}+\underbrace{222...2}_{n}=\underbrace{222...2}_{n}.2\underbrace{000...0}_{n-1}1 \\
& =\underbrace{222...2}_{n}.3.\underbrace{666...6}_{n-1}7=\underbrace{666...6}_{n-1}6.\underbrace{666...6}_{n-1}7 \\
\end{align}