Answer:
The equation is: 2/7x + 3 = 9
The unknown number is: 21
Explanation:
Write as an unknown value (using a variable)
2/7ths of a number = 2/7x
Write as an equation
2/7x + 3 = 9
Subtract 3 from both sides of the equation
2/7x = 6
Divide both sides of the equation by 2/7
x = 21
The equation is: 2/7x + 3 = 9
The unknown number is: 21
Hope this helps :)