A x 7 + A x 9 - A - A x 5 = 290
A x 7 + A x 9 - A x 1 - A x 5 = 290
A x ( 7 + 9 - 1 - 5 ) = 290
A x 10 = 290
A = 290 : 10 = 29
A x 7 + A x 9 - A - A x 5 = 290
A x 7 + A x 9 - A x 1 - A x 5 = 290
A x ( 7 + 9 - 1 - 5 ) = 290
A x 10 = 290
A = 290 : 10
A = 29