strike a balance		in doubt
upset		off (something)
to be off		behind the idea
the brains		hair
come to/arrive at/reach		by your principles
cast doubt		a bell
to be		out
make a mental note		for the trees
mental arithmetic		arithmetic
have a one-track mind		into account
take (one's) mind off (something)		up on English
under		to stand on
to stand		for exams
not have a leg to stand on		between sth and sth
don't see the wood		the balance
ring		balance
brush		a mental note about sth
piece		a misapprehension
cram		the balance
split		a conclusion
puzzle		on something
take something		track mind
hang in		sth together