Answer:
4
Step-by-step explanation:
We want to find the highest common factor
Breaking them into factors
28 = 4*7 = 2*2*7
40 = 4*10 = 2*2*2*5
12 = 4*3 = 2*2*3
24 = 3*8 = 3*2*2*2
The factor that appears in all is 2*2
2*2 =4
28÷4=7
40÷4=10
12÷4=3
24÷4=6
7, 10, 3 and 6 cannot be divided by any same number.
