Which expression is equivalent to 3√50 × √22 ? Please show work :)

A. 15√22
B. 30√22
C. 30√11
D. 15√11

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?

The radius of the earth is two times the radius of the moon. what fraction of the volume of the earth is the volume of the moon?

3x + 4y = 5 x- 3y = -7 solve by substitution