Verified Answer :

\(G=H(q+Q)\\ q+Q=\frac{G}{H}\\ Q=\frac{G}{H}-q\)

\(G=H(q+Q)\\\\H(q+Q)=G\\\\Hq+HQ=G\ \ \ \ \ |both\ sides\ -Hq\\\\HQ=G-Hq\ \ \ \ |both\ sides\ :H\\\\Q=\frac{G-Hq}{H}\)

\(or\\\\H(q+Q)=G\ \ \ \ \ |both\ sides\ :H\\\\q+Q=\frac{G}{H}\ \ \ \ \ |both\ sides\ -q\\\\Q=\frac{G}{H}-q\)