The expression is .

According to addition property of equality: if a = b, then a + c = b + c.

          (Add 25 to each side)

                           (Additive inverse property: )

k = 55                                    (Add: 30 + 25 = 55)

Check:

To check the solution Substitute the value of k = 55 in above expression.

30 = 30                                  (Subtract: )

The value of k = 55

By the number line k = 55