<PRE><B>Question 205272</B>
Final exam score = x


average score = {{{(68+65+75+78+2x)/6}}}
= {{{(286+2x)/6}}}
70 &amp;#8804; average score &amp;#8804; 79
{{{70&lt;=(286+2x)/6&lt;=79}}}
{{{70*6&lt;=(286+2x)&lt;=79*6}}}
{{{420&lt;=(286+2x)&lt;=474}}}
{{{(420-286)&lt;=2x&lt;=(474-286)}}}
{{{(420-286)&lt;=2x&lt;=(474-286)}}}
{{{134&lt;=2x&lt;=188}}}
divide them by 2:
{{{67&lt;=x&lt;=94}}}

</PRE>