The total mass of cells in a petri dish is 3 × 10–2 gram. The mass of each cell is 4 × 10–5 gram. How many cells are in the dish?
A. 7.5
B. 7,500
C. 75
D. 750

Ineed to know the answer to this algebra question.

Mr. brettler is hanging up a 5-foot tall rectangular welcome sign in the gym. he has drawn a sketch on a coordinate grid. he has the lower vertices of the sign at (9, –3) and (–6, –3). where would the upper vertices be on the grid?

Aclassmate thinks that solving a system by graphing gives an exact answer when the lines appear to cross at a grid point, but only an approximate answer when they don't. explain why this isn't true.