有三个数，甲数和乙数的平均数是75，乙数和丙数的平均数是69，甲数和丙数的平均数是81，甲、乙、丙这三个数的平均数是多少？
直接写出得数．= = == = == = =
直接写出得数．÷= 0×= ÷= 1+=×= ÷= ×= ÷=
直接写得数．×8= ÷= = 6÷=÷= 21×= 1﹣÷= ×=
直接写出得数．1÷100÷10= 1﹣= +1÷3= 6×=60%÷12= ×= ÷= 500×3%=
直接写出得数：×8= ÷2= ÷= ×=×= 1÷= ÷60%= ×15=﹣= 6.8÷10%= 4.5+= ×=
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= 
=
÷
= 
÷
= 1+
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×
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÷
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×
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÷
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×8= 
÷
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= 6÷
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= 1﹣
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×
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+1÷3= 6×
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×
= 500×3%=
×8= 
÷2= 
÷
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×
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×
= 1÷
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÷60%= 
×15=
﹣
×
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