Question 939044
grades on first 5  maths exams  = 89,79,82,91 &92
  sum  of grades on 5 exams  = 89+79+82+91+92 
                         = 433
    let x be the grade on last exam
   hence total  =  433+x
  average  = 75
  {{{(433+x) /6= 75}}}
     {{{ (433+x)  = 6*75}}}
    {{{ 433+x=  450}}}
     x= 450-433
      x= 17 
 Hence he should get at least  17  marks on last exam