I would describe the formula first:BMI = weight in kg/height in m^2
Now look at the number of marks offered = 3. Means you need to show your working, calculate the BMI accurately, and IMPORTANTLY, include the 3.s.f. to get the last mark.
substitution (1) 72÷1.81^2evaluation (1)= 21.977 / 21.98 / 22 3 s.f. (1) 22.0