C. -2° :) hope this helps lmk!
Answer:

Step-by-step explanation:
Given
-- degree of freedom

Required
Determine the t-value
The given parameters can be illustrated as follows:

Where

So, we have:

To solve further, we make use of the attached the student's t distribution table.
From the attached table,
The t-value is given at the row with df = 28 and
is 3.673900
Hence, 
Answer:
Step-by-step explanation:
plug y into the first equation:
8x+5y=24
8x+5(-4x)=24
8x-20x=24
-12x=24
x=-24/12
x=-2
then plug x to the second equation
y=-4
y=-4(-2)
y=8
x=-2
y=8