[tex]\displaystyle\bf\\S~note:\\S_n=n_1+n_2+n_3+n_4+n_5=35\\\\Media~aritmetica~a~notelor:\\\\m_a=\frac{n_1+n_2+n_3+n_4+n_5}{5}=\frac{35}{5}=7\\\\Media~pe~semestrul~este~o~medie~ponderata.\\Media~aritmetica~a~notelor~(m_a)~are~ponderea=3\\Nota~din~teza~(teza)~are~ponderea~1\\\\Media~pe~semestrul~II~(m_{s})~este:\\\\m_{s}=\frac{m_a\times3+teza\times1}{3+1}\\\\m_{s}=\frac{7\times3+teza}{4}\\\\7,75=\frac{21+teza}{4}\\\\21+teza=7,75\times4\\\\21+teza=31\\\\teza=31-21\\\\\boxed{\bf teza=10}[/tex]