IS POPPING MY KNEE SAFE?

In which book word demography is used for first time

Asubstitute is standing at the halfway line waiting to enter the match at the next stoppage of play the ball has gone over the touchline for throwing and referee allows for the substitution to substitute wants to take the throw-in does the substitute first have to enter the field of play before being allowed to take the throw-in

To interpret the problem and solution in a problem-solution text, the reader should look for words that relate to