Answer :
*Hint: To make this easier, you might want to give all of them common denominators.
4/7 = x + 3/21
12/21 = x + 3/21
9/21 = x
And then simplify it.
x = 3/7
4/7 = x + 3/21
12/21 = x + 3/21
9/21 = x
And then simplify it.
x = 3/7