Q.20 and 21 please solve

20.    Mukesh's home is 6.87 km away from school. Anuj's home is 3.5 km less than 7 times as far as Mukesh's home from school. Find the distance between Anuj's school and his home.

21.  The approximate length of diagonal of a square can be found by multiplying the length of a side of the square  by 1.414. Find the length of the diagonal when :

a)    The length of a side of the square is 3.3 cm.

b)    The length of a side of the square is exactly 4.25 cm.