I'll do this first one completely:

One dress uses meters of cloth, so three dresses will use meters. So if she started with meters of cloth, she will have

meters of cloth remaining.

Let the number of men, women, and children, be respectively.

Then we know that and that .

But you also know that . Substitute this into the second relation, and you can solve for the number of women. Then substitute that back into the first equation and you will be able to solve for the number of men.

We will have to assume that these books are all the same price. Let that price be .

Suppose Limin has units of money (dollars, pounds, euros, whatever--makes no difference here). Then we know that two-fifths of this amount will total to the cost of 40 books: .

Solving for : . Now, of her money will buy books: . Substitute for and solve for .

(Of course, if you wanted to be picky, the initial relation should actually be ; the answer should work out the same)