I'm in agreement with the prior answer, slow a bit, let the gap grow and then resume previous speed.
Now I've got one ... you and another boat are on an apparent collision course. He's coming from your port side, very nearly at right angles. You are thus the priveledged vessel and he should give way. Then he turns slightly to his port so your course is now slightly aft of beam. Since you left your protractor at home it's not clear if the crossing angle is more or less than 112.5 deg but you're right in that area.

What do you do ?