Guess by 18yo, your DS is all ready for NS training compared to his peers under your “brute force”. 🙂
My way to my little audience at home* –> I tell DC that I am too lazy to take back all those sweets already distributed (6pcs each). So to give each student 3 pcs more (9-6=3), I will need to grab those 4 pcs leftover and use my “Elder wand” to get the 32 pcs that I am short of, put all in a bag (4+32), then give each student 3 pcs more (divide by 3) until I have no more on hand.
Most times, when talk about less work, more food, pizza, sweets and Harry Potter etc, my audience at home can get the Maths working. I think DDs would appreciate more “elegance” than “brute force”.
*Actually this is the common excess/shortage method. But I avoid to quote it as “excess/shortage” with formula while teaching my kids but always fall back to basic understanding of scenario.