For this case we must find an expression equivalent to:

To express in scientific notation we must take into account that the power will be positive, that is, the decimal is run to the right.
We test each option.
Option A:

If we run the decimal 9 spaces to the left we have:

Option B:
We discard it because the exponent is negative.
Option C:

We run the decimal 6 spaces to the right

Option D:

We run the decimal 9 spaces to the right

Answer:
Option D
Answer:
1.76
Step-by-step explanation:
3.9-7.4x=-4.5x+9
-2.9x=5.1
x=1.758 or 1.76
I hope this helps, if not i'm sorry.
It is angle 4 because they make 90 degrees together