The average temperature for Wednesday, Thursday and Friday was 40^oC. The average for Thursday, Friday and Saturday was 41^oC. If temperature on Saturday was 42^oC, what was the temperature on Wednesday?

Explanation:-

Average temperature for Wednesday, Thursday and Friday = 40^oC
Total temperature = 3*40 = 120^oC
Average temperature for Thursday, Friday and Saturday = 41^oC
Total temperature = 41*3 = 123^oC
Temperature on Saturday = 42^oC
Now,
(Thursday + Friday + Saturday) - (Wednesday + Thursday + Friday) = 123-120;
Saturday - Wednesday = 3
Wednesday = 42-3 = 39^oC.