78+91+82+79+x)÷5=x-6 ,
(330+x)/5=x-6,
330+x=5(x-6),
330+x=5x-30,
4x=360,
x=90
(78+91+82+79+x)÷5=x-6
((78+82)+(91+79)+x)÷5=x-6
(160+170+x)÷5=x-6
330÷5+x÷5=x-6
66+x÷5=x-6
72=x-x÷5=4x÷5
x=72×5÷4=90
(78+91+82+79+x)÷5=x-6
331+x=5(x-6)
331+x=5x-30
5x-x=331+30
4x=361
x=361/4
(78+91+82+79+x)÷5=x-6
(330+x)÷5=x-6
330+x=5x-30
4x=360
x=90