I hope it helps you get it right
Answer:0.369 m
Step-by-step explanation:
Given
Distance between slit and screen is 
Wavelength 
Angle between zeroth order bright fringe and Fourth-order bright fringe is 
let distance between the slits be d
Distance of n th bright fringe From central Fringe is given by

Also 



Answer: -5/21
Step-by-step explanation:
-3/7 & -4/6
common detonator is 42
-3/7 = -18/42 reduced to -9/21
-4/6 = -28/42 reduced to -14/21
difference between -9/21 and -14/21 = -5/21