:
what is 58,000,000,000 estimated as the product of a single digit and a power of 10?

If we multiply and then divide the number by the same thing,
we won't change its value.

Take the number:    58,000,000,000

Divide it by  10¹⁰ :    5.8

Multiply it by 10¹⁰ :   5.8 x 10¹⁰

They want a single digit, so we'll round the 5.8
to the nearest whole number:

                                   6 x 10¹⁰ .