Answer :
[tex]A=\frac{1}{2}(b+c)h\ \ \ \ |Divide\ by\ h\\\\
\frac{A}{h}=\frac{1}{2}(b+c)\ \ \ \ |Multiply\ by\ 2\\\\
\frac{2A}{h}=b+c\ \ \ \ |Subtract\ b\\\\
\frac{2A}{h}-b=c\\\\Solution\ is\ c=\frac{2A}{h}-b.[/tex]
[tex]A= \frac{1}{2} (b+c)h \\ \\ 2A=(b+c)h \\ \\ \frac{2A}{h} =b+c \\ \\ \frac{2A}{h}-b=c[/tex]