Respuesta :

[tex]A=\frac{1}{2}h\times(b+c)\ \ \ \ \ |multiply\ both\ sides\ by\ 2\\\\h\times(b+c)=2A\\\\hb+hc=2A\ \ \ \ \ |subtract\ hc\ from\ both\ sides\\\\hb=2A-hc\ \ \ \ \ \ |divide\ both\ sides\ by\ h\\\\\boxed{b=\frac{2A-hc}{h}}[/tex]