A student in the laboratory measures thickness of a wire using...

The average value of the readings is ${x}_{avg} = \dfrac{1 . 19 + 1 . 20 + 1 . 22 + 1 . 23}{4} = 1 . 21$

Now, absolute error in measurement $\Delta{x}_{avg} = \dfrac{0 . 02 + 0 . 01 + 0 . 01 + 0 . 02}{4} = \dfrac{0 . 06}{4} = 0 . 015$

Percentage error in measurement is $= \dfrac{0 . 015}{1 . 21} \times 100$$= \dfrac{150}{121}$

So, the value of $x = 150$.