I'm not going to do a very complicated explanation.
23. 24*2 = $48 paid ( -48 gained)
If each pastry costs 2 dollars, and he bought 24 pastries, then that is a total of $48 paid for all of the pastries.
24. -5*7 = -35* from today (35* colder)
If each day gets 5* colder, and this happens every day for 7 days, then it will be 35* colder than today in 7 days.
25. -60*6= -360 feet from sea level (360 ft. below sea level)
If the submarine travels -60 ft. from sea level each hour for 6 hours, then it will have traveled -360 ft. from sea level after 6 hours.
26. 10*40 = 400 meters fallen (-400 meters from original place)
If he is falling ~10 meters per second for 40 seconds, then he will have fallen approx. 400 meters in those 40 seconds.