−3x + y = 4,

−9x + 5y = −1

Step-by-step explanation:

Option 1:

−3x + y = 4eq. 1

−9x + 5y = −1eq. 2

from eq. 1,

we get y = 4 +3xeq. 3

substitute eq. 3 into eq. 2.

-9x + 5(4 +3x) = -1

-9x + 20 + 15x = -1

-9x + 15x = -1 – 20

6x = -21

x = –3.5

to solve y, use the obtained x in eq. 3,

y = 4 + 3(–3.5)

y = -6.5

256π units²   (answer b)

step-by-step explanation:

the formula for the surface area of a sphere of radius r

is             a = 4πr²

and so, if r = 8 units, then the surface area is:

a = 4π(8 units)² = 256π units²   (answer b)