The part of the sentence “half a number” refers to x/2 because you are taking a number x and dividing it by 2. Then you have that number minus 7 so you now have x/2 - 7. Finally the sentence says that it is “one and five tenths” so it is saying that it is equal to 1.5 leaving your equation to be x/2 - 7 = 1.5
Answer x/2 - 7 = 1.5