There are two triangles: triangle MAB and triangle MNP
The slanted sides on the right side of the triangles are MB and MP. They correspond to one another. So they form a ratio MB/MP. I have the smaller piece up top. So we'll have the smaller piece of MAB's other known side which is MA = 35.2 (subtract 67.22 and 32) and we'll divide MA over MN = 67.2 making the ratio MA/MN
One half of a number represents the phrase "1/2a" (in this case the variable/number is 'a'". Then because it says "nineteen less than", that means you subtract 19 from one half of the variable.