Please help i will give brainliest if correct

Is the square root of 4 plus the square root of 16 rational?

9.4.34  question   to estimate the height of a stone  figure, an observer holds a small square up to her eyes and walks backward from the figure. she stops when the bottom of the figure aligns with the bottom edge of the  square, and when the top of the figure aligns with the top edge of the square. her eye level is 1.811.81 m from the ground. she is 3.703.70 m from the figure. what is the height of the figure to the nearest hundredth of a  meter?

Solve for x: 5/3 x = 20/21 it's fraction. remember to simplify your fraction