Digit-Related Problems

$100h + 10t + u$ = the number
 

The hundreds digit is twice the units digit
$h = 2u$       ← equation (1)
 

The sum of the digits is 17
$h + t + u = 17$       ← equation (2)
 

396 be subtracted from the number
$(100h + 10t + u) - 396 = 100u + 10t + h$

$99h - 99u = 396$

$h - u = 4$       ← equation (3)
 

Substitute h = 2u to equation (3)
$2u - u = 4$

$u = 4$
 

From equation (1)
$h = 2(4)$

$h = 8$
 

From equation (2)
$8 + t + 4 = 17$

$t = 5$
 

The number is
$100h + 10t + u = 854$           answer