What is 4x10 to the power of 2 in standard notation?

4x10²
You can either do this by solving,
4 × (10 × 10)
4 × 100
400

Or you can do it by just moving the (invisible) decimal point after 4, 2 spaces to the right (because the exponent is positive.
4.00
400

So in standard notation, it's 400.