Si Don Carlos tiene una parcela rectangular en la cual el largo mas el ancho mide 30 m y la diferencia entre el largo y ancho es 6 metros¿ cuanto mide el ancho de la parcela?(algebra)

Several paint mixtures are made by mixing blue paint and white paint. paint colors blue paint white paint mixture a 5 cups 12 cups mixture b 6 cups 6 cups mixture c 4 cups 12 cups mixture d 5 cups 6 cups which mixture has the highest ratio of blue paint to white paint