## mass = 45/g

change in weight = 45 -15 = 30 N

so

mass of water displaced = 30/g

volume of water displaced = 30/g / water density

which is volume of the solid since it is totally submerged

so

mass of solid / volume of solid

= (45/g) /[(30/g)/water density]

= (45/30)*water density

so

density relative to water = 45/30 = 1.5