Get the surd by itself, then square and solve the resulting linear equation.
1. Subtract 2, then square
... √c = 25
... c = 25² = 625
2. √x = 3
... x = 3² = 9
3. √(x-2) = 4
... x -2 = 4²
... x = 16 +2 = 18 . . . . add 2
5. √(2x) = 1
... 2x = 1²
... x = 1/2 . . . . . . . divide by the coefficient of x