It is at the intersection of the signal ray ( lines) from both the ship.
For ship 1 the equation of the line (signal ray) is x = 4 ---------------(1)
and for the ship 2 the line equation is
y = -tan45 * x + 6 = -x+6 (slope-intercept form) ------------------------(2)
The intersection is (substitute x = 4 in the second equation giving y = -4 + 6 = 2
Therefore the coordinates of the ship in distress = (4,2)