Gente quanto é g)3x=12 h)9x=18 i)35x=-105 j)7x-1=13 e a letra a b c etc eu já fiz

Long division setup showing an incomplete calculation. 12 is in the divisor, 6839 is in the dividend, and 5 hundreds and 6 tens is written in the quotient. 6000 is subtracted from 6839 to give 839. an unknown value represented by a box is being subtracted from 839. what number should be placed in the box to complete the division calculation?