Ответ:

а) \(19.1y+0.9y+121.4=20y+121.4\). При \(y=48.5\): \(20\cdot48.5+121.4=970+121.4=\boxed{1091.4}\).

б) \(5.6m+8m+186.4=13.6m+186.4\). При \(m=35.5\): \(13.6\cdot35.5+186.4=482.8+186.4=\boxed{669.2}\).