A tangent line is perpendicular to the radius of a circle, so the triangle here is a right one. The Pythagorean theorem can thus be used to find the unknown segment length: take the square root of the difference between 100 and 64, and you get x = 6, which is your answer.
Say you have the equation 5(5x+7)=155 First you multiply 5 by everything in the parenthesis so you get 25x+35=155 then subtract 35 from both sides and get 25x=120 then 120 divided by 25 equals 4.8 so x=4.8
