1, a three-digit number, the hundred digits are twice as many as the ten digits, and the ten digits are twice as many as the single digits. If you exchange the hundred digits with the single digits, you get 396 less. So what is this three-digit number?

2.if( 1/3)(X-500)+( 1/7)(X-500)+( 1/ 10)(X-2 1)+(65438)

3.if[( 1/9)(x+ 1)+( 1/ 13)(x- 1)+46]/ 12 =( 1/0)