Please help me I have a timed quiz

An object weigh 40n in air ,weigh 20n when submerged in water,and 30n when submerged in a liquid of unknown liquid density.what is the density of unknown of liquid?

Hi , i am new here can anyone me out with this question why is space black after having so many shining objects like sun , moon , stars

Mrs. smith does her daily chores. she walks 5 m to the laundry room and then turns around and walks -14 m to the kitchen. the whole process takes her 11 minutes. what was her average velocity for these events? (choose more than 1) a. 1.48 m/s b. 0.212 m/s c. -0.136 m/s d. -0.0075 m/s