Abox of marbles can be shared equally among 6,7, or 8 students with 4 marbles left over each time. what is the least possible number of marbles in the box

Im pretty sure the answer is 12 because
6+4=10
7+4=11
8+4=12 
so the least amount would be 12

38+105= 143, 39+104=143, and you will find then adding the numbers on opposite sides, moving inwards yields the answer 138 every time. because of this, you’re going to multiply 138 times the number of pairs, which is 34. therefore, 34*138= 4692(i’m sorry if it’s the wrong numbers, but it’s the right concept)