Can anyone please help me with this one ?:)

Write a corresponding real world problem to represent 2x - 125=400

To determine the number of deer in a forest a forest ranger tags 280 and releases them back

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?