Answer:
24
Step-by-step explanation:
We are solving for variation (without repitition)
n = 4 digits (6,7,8,9)
p = 3 digits no.
variation = nfactorial/ (n-p) factorial.
4x3x2x1/(4-3)factorial = 24/1
= 24.
there are 24 3-digit number you can select from 6,7,8,9 without having a recurring number.