Question

the sum of a number and it's one third is 20. find the number

Answer 1

Let no. Is x then x+1*x/3=20
4x=60 and
X= 15

Answer 2

$x + \frac{x}{3} = 20 \\ 3x + x = 60 \\ 4x = 60 \\ x = \frac{60}{4} \\ x = 15$