tolong dong pliss :( pake cara ya

rata" = 7
7 =((5x6) + (6x8) + (7x10) + (8x) + (9x4))/(6+8+10+x+4)
7 = (30+48+70+8x+36)/28+x
7(28+x) = 184+8x
196+7x = 184+8x
196-184 = 8x-7x
12 = x