9)

11)
(a²b)³ = a²⁽³⁾b¹⁽³⁾ = a⁶b³
12)
The exponent tells you how many places to move the decimal. The positive/negative sign tells you which direction to move the decimal (negative is left, positive is right).
8.4 x 10⁻⁵ <em>move the decimal 5 places to the left</em> = 0.000084
x=2, y=3 is a pair of a equations right there, so a correct solution.
How about another linear system?
Answer: x+y=5, 10x + y = 23
Answer:
x=3
Step-by-step explanation:
6x-3
(6*3)-3
18-3
15
3x+6
(3*3)+6
9+6
15
5x
5*3
15
12. hope that helps you with your homework