He's reading at a rate of 1/3 chapter per night and if there 2 1/3 chapters left to read we can divide the chapters left by his reading rate (2 1/3 ÷ 1/3 = 7 nights).
Another way to solve this problem is to make an equation to show the situation with x being the number of nights reading.
1/3x=2 1/3
<em>Solve for x by dividng 1/3 from each side of the equation.</em>
x=7
So he must read for 7 nights to finish the chapters that are left.
