15 POINTS pre algebra I think

28.6 (90% sure)

Step-by-step explanation:

To solve this work backwards

=42

=42*.80 = 33.6

=33.6-5 = 28.6

false

step-by-step explanation:

the reason i say this is because for a certain length of sides you can pick any two and the length is wither equal or greater than the third side and in this case it's not.

3 + 5 = 8

8 is smaller than 9 which is the third side.

hope this : )