The average number of p，q，r is 4，and average number of p，q，r，x is 5，then x=______．
（英文詞典：average number平均數(shù)）
∵p，q，r的平均數(shù)是4，
∴P+q+r=4×3=12，
∵p，q，r，x的平均數(shù)是5，
∴p+q+r+x=5×4=20，
解得x=8．
故答案為：8．
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