First,since we know that the total of 3 presents is 57,we divide 57 by 3 which would give us 19, so the value of the present is 19.

Then,knowing that the value of 1 present is 19,and the total of 1 present and 2 pens is 47,2 pens are 47 - 19 which is 28 and the value of 1 pen is 28 divided by 2 is 14.

since we know the alue of 1 pen and the total of 2 pears and 1 pen is 26,we can find the value of 2 pears.26 - 14 is 12.12 divided by 2 is 6,so the value of a pear is 6.