The average of seven numbers is 18. If one more number is added, the average becomes 20. Find the eighth number.

7 संख्याओं का योग = $7 imes 18 = 126$। 8 संख्याओं का योग = $8 imes 20 = 160$। आठवीं संख्या = $160 - 126 = 34$।