The correct answer to this is that 2.3 -20=-17.7
the answer is resonable because if you go on a number line then you would see that if you start a 2.3 and subtract 20 spaces you get to ----17.7
If 20-2.3=17.7, then if you add 17.7 to 2.3. it equals 20 which is called the communicative property because whatever you add or subtract, the answer is the same 17.7+2.3=2.3+17.7
