345 is 60% of what number?
390 is 35% of what number?
280 is 70% of what number?
330 is 45% of what number?

The two-way frequency table below shows data on playing a sport and playing a musical instrument for students in a class.

Create and solve a linear equation that represents the model, where squares and triangles are shown evenly balanced on a balance beam. assume the weight of a square is 1 unit and the weight of a triangle is unknown.

The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20. according to the standard deviation rule, how much did almost all (99.7%) of the students spend on textbooks in a semester?