Context Free Grammar $L = \{a^i(b+c)^jd^k | i0\}$
Whenever you see a condition $i&lt;j+k$, you can translate that to the condition $i+\ell=j+k$ where $\ell&gt;0$, then use the methods you know for handling $=$ instead of $&lt;$.

See our reference question on this subject for more systematic answers.