Question 922706
In arithmetic progression, rule is as follows
            {{{ middle term  = (sum of first term +last term)/2}}}
              {{{ (5k-11) = ((2k+2)+(7k-13))/2}}}
                  multiply with 2 on both sides
                    {{{ (5k-11)*2 = (((2k+2)+(7k-13))/2)*2 }}}
                             {{{ (5k-11)*2 = 2k+2+7k-13}}}
                             5k*2-11*2 = 9k-11
                              10k-22=9k-11
                                   move 9k to the right
                    10k-22-9k= -11
                            k-22 =-11
                              move -22 to the left
                               k =-11+22
                               k =11
 result k =11