Question

read the sentence.
the coded log book proved decipherable with the help of a few simple equations.
based on the suffix, -able, what does the word \decipherable\ mean?
able to be seen
able to be counted
able to be understood
able to be discussed

Explanation:

The suffix -able means "capable of being". The root word "decipher" means to convert coded text into understandable language, so "decipherable" means capable of being deciphered/understood. The context of a coded log book being made clear with equations also supports this.

Answer:

able to be understood