Homework help? please. thanks so much!♥

You have to use BEDMAS (Brackets, Exponents, Division, Multiplication, Addition, Subtraction)
That's the basic format and the order you should simplify your question with.

5.6 x 1018 * 7.4 x 1020 =
5.6 x 7533.2 x 1020 =
42 185.92 x 1020 =
=43029638.4
So first I dealt with the exponents which was 1018 * 7.4 and then I just did simple step by step work

2.0 x 1010 /4.0 x 109 = ?
Start off with division since that's the first thing that you see pertaining to BEDMAS because theirs are no brackets nor are there any exponents.
2.0 x 252.5 x 109 =
Continue with regular multiplication
55045

7.6 x 1023 + 4.4 x 1021 = ?
BEDMAS the first thing you see in the equation is multiplication
7774.8 + 4.4 x 1021=
7938070.8 + 4.4 = 7938075.2

I hope you understand this =)