Answer:
-3, -2 1/2, -0.8, -1/10, 0.1, 0.5, 0.8, 7 
Step-by-step explanation:
Negative numbers are considered smaller than positive ones.  Separate the negative numbers from the rest, on the left side:
-0.8, 0.8, -0.1, 0.5, -3, -2,1/2, -1/10, 7 =>  -0.8, -0.1,  -3, -2,1/2, -1/10, 7, 0.8,  0.5
Now rearrange the negative numbers from smallest to positive and the positive numbers from smallest to largest:  
-3, -2 1/2, -0.8, -1/10, 0.1, 0.5, 0.8, 7