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1. I paid 7.80€ for 2 pens and 3 notebooks. Another day, I paid 13.20€ for 5 pens and 4 notebooks. How much does each pen cost? And each notebook?

      a pen costs x €, a notebook costs y €

       A pen costs 1.20 € and a notebook costs 1.80 €

2. The sum of the ages of a mother and her son is 56 years. Ten years ago, mother’s age was five times her son’s age. How old is each one?

  Mother is 40 years old and his son is 16



Exercises: solve the following problems:

1.- A bookseller sold 45 books last week, some of them at 32 € and the others at 28 €. If he collected 1368 €, how many books of each kind did he sell?

2.- We have mixed olive oil at 3.5 €/l with sunflower oil at 2 €/l, to obtain 50 l of mixture for 3.08 €/l. Calculate how many litres of each kind of oil we have mixed.

3.- If we subtract a number of two digits to the number that results if we swap both its digits, the difference is twice the ten digit of the initial number. Calculate the number knowing that the total of its digits is 16.




Solutions: 1) 27 at 32 € and 18 at 28 €; 2) 36 l of olive oil and 14 l of sunflower one; 3) 97