Please help with problem and show work

x = 7

Step-by-step explanation:

The image below shows the relationship between secants chords and tangents.

Imagine that the letters in the image represent the numbers in the actually problem

E would equal 9

C would equal 12

and A would equal x

We would then use the same formula C² = E * ( E + A ) to solve for x , but once again instead of using letters we use the numbers in the problem

We would have 12² = 9( 9 + x )

we now solve for x

Step 1 simplify and distribute

12²=144

9 * 9 = 81

9 * x = 9x

we would then have 144 = 81 + 9x

step 2 subtract 81 from each side

144 - 81 = 63

81 - 81 cancels out

we now have 63 = 9x

step 3 divide each side by 9

63 / 9 = 7

9x / 9 = x

we're left with x = 7