Heres an easy way to think about it
If we make 2/3 into 6/9 by multiplying by 3, then all you have is 6/9 + y - 1/6 = 7/9. But how about we even take away the /9, to make it even easier! 6 + y - 1 = 7. Now, we just think what's one more than 7? and that's 8 of course! and 6 plus what is 8?? 2! then we just put the /9 back, and your finale answer is 2/9. Now we just sub that in for 7!
6/9 + 2/9 - 1/9 = 7/9
8/9 - 1/9 = 7/9
the Equation is true, so our answer is correct.