Ok this is probably the easiest part in physics so lol dont panic. now the way you round is by looking at the exponent which in this case for the first one is -9 so 6.8 is gonna be 0000000068. because when you have a negative exponent you move the decimal to the west side. when you have a positive decimal you move to the east side. I will not do the second one because its best if you try to solve it so you can learn it. good luck my friend.
