The solving steps to complete this equation

Which of the following of the following sets of side lengths could not form a triangle?

Use corrrct notations to name the sides

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