Question

como resolver 7 x + 9=100 - x -3

Answer 1

Resolver.

7x + 9 = 100 - x - 3
7x + 9 = 97 - x
7x + x = 97 - 9
8x = 88
x = 88/8
x = 11

Respuesta.
x = 11

Answer 2

7x + 9 = 100 - x - 3

7x + 9 = 97 - x

7x + x = 97 - 9

8x = 88

x = 88/8

x = 11

Solución : 

x = 11

VERIFICAMOS

7x + 9 = 100 - x - 3

7 (11) + 9 = 100 - 11 - 3

77 + 9 = 100 - 14

86 = 86

Listo!!!