Answer:
[tex]\sf x = 6[/tex]
solving steps:
[tex]\sf in \ a \ rhombus \ the \ opposite \ angles \ are \ equal[/tex]
[tex]\hookrightarrow \sf 7x + 4 = 9x - 8[/tex]
[tex]\hookrightarrow \sf 7x -9x = - 8-4[/tex]
[tex]\hookrightarrow \sf -2x = - 12[/tex]
[tex]\hookrightarrow \sf x = 6[/tex]
