1+ 2k = 5k + 7 i got k=2 don't know if it's the right answer ?

You are close, but it is not the correct answer.

1 + 2k = 5k + 7

First, since we are trying to get the variable by itself, we need to move all things to one side. Let's subtract 1 from each side. 


Second, we can now subtract (7 - 1) to get 6. Let's add that into our problem and then subtract 5 from each side, still trying to get the variable by itself.


Third, subtract (2k - 5k) to get -3k. Hint the negative symbol now. If the problem were switched the other way, it would still be a positive. 


Fourth, we can now divide each side by -3. This results in a fraction and also getting the variable by itself on one side of the problem. Remember the negative sign in front of the fraction since (-3) carried it.


Fifth, this is our last step. We need to simplify the fraction. Since out fraction is 6/3, which number multiples by 3 to get the answer of 6? The answer is 2, since (3 × 2 = 6). Don't forget the negative!