Let's solve in <math><mi>ℝ</mi></math>: <math><msqrt><mi>x</mi></msqrt><mo> = </mo><mn>3</mn></math>
Since, by convention, the square root of a number is always positive or zero:
 <math><mi>x</mi><mo> = </mo><msup><mrow><mn>3</mn></mrow><mrow><mn>2</mn></mrow></msup></math>

▷<b>Answer: &nbsp; <math><mi>x</mi><mo> = </mo><mn>9</mn></math></b><span style='font-size:smaller'> &nbsp; &nbsp; (processing: 3 steps, 2 ms)</span>