move the decimal to the right ONE time because you basically have to simplify to the point that the digit is a one digit number (less than 10) and generally math teachers let you round off so i say go up to the thousandths place and round. in this case it would become 7.772 x 10^1
if your teacher puts units on the test for some reason PUT UNITS IN YOUR ANSWER and there is a difference in adding/subtracting etc. but if you're using the calculator it doesnt really matter for you as long as you enter it right. if you cal.doesnt have parenthesis go PIECE BY PIECE using PEMDAS. its SUPERRRRR easy once you get the hang of it (next step, i predict, will be your teacher asking you to do the opposite, she'll give you a number in scientific notation and ask you what it originally was)
sorry this was so long, please dont hate me, but i really hope this helped and good luck! try the rest on your own now :) im sure you'll get it