Last month nick spent $50 this month he spent 60% of last month how much did nick spend

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?

Select the conic section that represents the equation. 3x2 + 3y2 -2x + 4 = 0

According to the general equation for conditional probability if p(anb)=3/7 and p(b)=7/8 what is p(a i b)