since m is a midpoint, AM and MB are congruent so you set the two equations equal to each other, 4x-9=5x-3/3( is this a typo? bc 3/3 is 1) subtract 4x from both sides m, -8=x-1 add 1 to both sides x=-7
then plug -7 in for x 4(-7)-8=-36 since the two segments are congruent u do -36 x 2= -72
