Ta ó: \(\frac{6.5+8a+9.3+10.1}{5+a+3+1}=7,5\)
\(\Rightarrow\frac{67+8a}{9+a}=7,5\)
\(\Rightarrow67+8a=7,5\left(9+a\right)\)
\(\Rightarrow67+8a=67,5+7,5a\)
\(\Rightarrow8a-7,5a=67,5-67\)
=> 0,5a = 0,5
=> a = 1
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