i have problems with understand what they are asking in a word problem it goes like this

one jar holds 4mls more than twice. The two jars together hold the volume of the other jar. both jars together hold 712ml what is the volume the smallest jar hold.

Your problem is not worded properly.

The first sentence is incomplete.

1st Jar holds X mL.
2nd Jar holds (2x+4) mLs.

X + (2x+4) = 712 mL.
3x + 4 = 712
3x = 712-4 = 708.
X = 236 mLs. = Vol. of smaller jar.