Answer:
1 .205 * 10^20
Explanation:
120,500,000,000,000,000,000
To change to scientific notation, move the decimal to the left until there is only 1 number to the left of the decimal
1 .20500000000000000000
We moved the decimal 20 places to the left so the exponent on the 10 is 20.
1 .20500000000000000000 * 10^20
We can drop the extra zero's at the end ( after the decimal).
1 .205 * 10^20