when you're doing scientific notation you move the decimal between two numbers to make the numer between 1-9.
a)
in this case you have 12,820,000 you move the decimal between 1 and 2 so you have 1.282 then you count the number of places you've moved the decimal, which is 7, therefore your answer is 1.282×10 to the 7th power.
b)
since its 3.5 times further you multiply 12,820,000 by 3.5 and you get 44,870,000. so you don the same thing you did before you move the decimal between 4 and 4, so you get 4.487 and since you moved the decimal and since you've moved that 7 places also you get 4.487×10 to the seventh power
it's easy once you understand it but mainly you've got to move the decimal in between two numbers, which is less than 9 and greater than 1.
