The price of 3 pairs of skis and 4 pairs of skates was $470. What is the price of a pair of skis and a pair of skates if the price of 2 pairs of skates is $10 more than the price of a pair of skis?

If you had 50 lb of flour that was all the cheaper flour, it would be 50 * 31 cents, or $15.50 for 50 lbs. Instead it was 40 cents or $20. So that extra $4.50 is due to the more expensive flour.

For every pound of more expensive flour the mixture will cost another 15 cents. This is because you're removing a pound of 31 cent flour and adding a pound of 46 cent flour that costs 15 cents more.

The extra cost is $4.50 which is 15 * 30. That is to say of 50 lbs, 30 lbs of 31 cent flour has been removed, and 30 lbs of 46 cent flour has been added.

So the 40 cents per lb flour is made of 20 lbs of 31 cent flour and 30 lbs of 46 cent flour.

Now let's prove this by doing it backwards. 20 * 31 cents is $6.20. 30 * 46 cents is $13.80. 6.20 and 13.80 is $20 for 50 lbs and $20/50 is 40 cents a pound