What does it mean to say the mass is conserved during a physical change ?

The total mass of the substance remains the same from beginning to end. The physical properties of the substance, such as size and shape, may change. The amount of matter in the substance does not change.

"i have always loved contemporary art and made it a general goal to work within the field. after a few nonprofit internships at museums and galleries, i decided to try the for-profit art world and was offered a job as the ad assistant at the magazine. i much prefer the pace of the for-profit art community and have stayed with the company for three years, with a promotion to an account manager last spring."

i just did this and got a 100.

they should be similar or the same