Start by remembering that the square root symbol gives the non-negative root. The equation says that √(x - 3) is 10. To remove the square root, square both sides: x - 3 = 10² = 100. Now isolate x by moving the constant to the other side, so x = 100 + 3 = 103. Always check radical equations: substituting x = 103 makes the expression inside the root equal to 100, and √100 = 10. So the correct answer is 103.