in this question we are calculating the elevation between two points. those are point A and B Reading At point A = 1.55 meters means the level is 1.55 meter higher then from the point of measure Reading at Point B = 1.95 meters means the level is 1.955 meter higher than from the point of measure. now as we have to find the difference between them so we simply do subtraction. that is B-A= 1.95-1.55 = 0.4 so the answer is 0.4 meters