Answer:
x = 10
Step-by-step explanation:
Use Pythagorean theorem to find the value of x
Focus only on one half of the triangle
if we slice the triangle in half, we get a right angle triangle
the base will now be 12/2 = 6
Pythagorean theorem says that 
plug 6 as a and 8 as b.
this should give you 100
now take the square root to find c (which equals x)
Ta-da!
Answer:
Negative line
Step-by-step explanation:
Going up is positive (think in going uphill)
Going down is negative
8(x - 6) = 4x
Distribute.
8x - 48 = 4x
Subtract 8x from both sides.
8x -8x - 48 =4x -8x
Now you have...
-48 = -4x
Divide -4 by both sides.
-48/-4 = -4x/-4
12 = x
The number is 12.