Three numbers are chosen at random.

The middle number is 4 more than the smallest number.

The largest number is two times the smallest number.

The sum of the 3 numbers is 54.

What is the smallest number?

So we have x, y, z

smallerst=x

middle=y

z=largest

so

middle is 4 more than smallest

y=4+x

largest is 2 time smallest

z=2x

sum (addition) of the three is 54

x+y+z=54

so subsitute

z=2x

y=x+4

x=x

therefor

x+y+z=54

x+x+4+2x=54

add like terms

4x+4=54

subtract 4

4x=50

divide both sides by 4

x=25/2=12.5

the smallest number is 12.5