You go from left to right and tell what each numeral represents write it as a factor of 10. The 1 is "one ten" because it is in the 10's place We can write that as 1 x 10¹ The 2 "two ones" which can be written as 2 x 10⁰ (anything to the zero power is 1) Negative powers of 10 will help us with the decimals
The 5 is "five tenths" or 5 x 10⁻¹ The 7 is "five hundredths" or 7 x 10⁻² Finally the 6 is "6 thousandths" or 6 x 10⁻³ Final answer in expanded form is: 1 x 10¹ + 2 x 10° + 5 x 10⁻¹ + 7 x 10 ⁻² + 6 x 10⁻³