A phrasal verb is a verb plus a preposition or adverb; the combination creates a meaning different from the original verb.

abide by:
(comply,follow,honour,respect,observe),show respect towards
Act in accordance with someone's rules, commands, or wishes
Use: "abide by the rules"
If you want to stay at this school, you must abide by the rules.

account for:
Be the reason or explanation for, Give reasons for
(be,explain,explicate)
Use: "The recession accounts for the slow retail business"
"Can you account for all these absences?"
can you account for the money you spent!

add up :
make sense, Develop into, Be reasonable or logical or comprehensible
Add up in number or quantity
Use: Her story just doesn't add up.

agree with:
have the same opinion as somebody else.
Use: I agree with you. I thank she deserves the award too.

avail of:
Take or use, Use to one's advantage, Be of use to, be useful to
Use: When the company is privatized, you should avail of the opportunity and buy some shares.
"He availed himself of the available resources"
"It will avail them to dispose of their booty"