Rsm problem pls help me

(originally answered by DeanR so credit to him)

x=6

Step-by-step explanation:

x3579x = 100000 x + 35790 + x

100000 = 2380 × 42 + 40

35790 = 852×42 + 6

Working mod 42,

100000 x + 35790 + x = 40 x + 6 + x =  41x + 6 = 6-x  (mod 42)

So basically we need 6-x to be a multiple of 42, so between 0 and 9 that's x=6.

So our number is

635796 = 15138 × 42

x=6

Step-by-step explanation:

All of the factors of 42 under are only 7 and 6. Substitute one of them for x. 7 is wrong so 6 is the answer.