Bowling Scores

In three bowling games, Alma scored 138, 141, and 144. What score will she need in a fourth game
​to have an average score of 145 for all four games?

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Add all of the games, including the missing game x, and divide by 4.  Set this equal to 145 and solve for x, to
determine the score needed to meet the desired average of 145.

x = needed score on fourth game

138 + 141 + 144 + x
——————————— = 145  {added all games, divided by 4, and set equal to average of 145}
               4

423 + x 
————— = 145  {added in numerator}
     4

423 + x = 580  {multiplied each side by 4}

x = 157  {subtracted 423 from each side}

157 is the score needed to get an average of 145

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