Hi dferm,
I think the easiest way to do this one is to plug in numbers. Let's say the first month, the whole family earned $100. Thus, Mrs. Lee earned $60, and the rest of the family earned $40.
Now, in the second month, Mrs. Lee earned 20% more, so $72. The rest of the family still earned $40, for a total of $112.
Now we just need to know what 72/112 is as a percent, and with a bit of division we come out to 64%.
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