Question

How many counting numbers have three distinct nonzero digits such that the sum of the three digits is 7?​

Answer 1

6

Explanation:

You have 2 conditions.

1. The digits must be different.

2. The digits must add to 7.

There aren't very many

124

142

214

241

412

421

That's it. That's your answer. There are 6 of them