Let's make an equation. x+y+z=72 X will be the smallest number. Since they are consecutive, one number is one greater and the other is two greater. Let's make equation for y and z. x+1=y; the middle number. x+2=z; the greatest number. Let's plug these in the equation. x+x+1+x+2=72 Let's add like terms. 3x+3=72 Subtract 3. 3x=69 Now divide. 69÷3=23 So, the smallest number is 23. So, it must be set a. Let's check. 23+24=47+25=72 So, set a is the correct answer.