This form of exercise is too, too common. You will find maybe hundreds of examples solved on the site.
A possible approach or method to begin:
r, speed if wind absent
w, speed of wind
SPEED TIME DISTANCE
GOING(with) r+w 11 1012
RETURN(against) r-w 22 1012
Basic rule so this means .
You have this system:
Simplify further and solve.