The perimeter of a regular pentagon is 10x + 20 . find the length of one side .

So this is called a one step equation so in that case...
you are wanting to isolate the variable  x so the length of one side is going to be x for this equation. So first you "have" to get x by itself  in order to do to that you will want to either subtract 20 from both sides which will leave you with -10 and you don't want that so you will have to divide 10 from both sides to get x=.5
I will attach what i did to get your answer in the attachment below.  Hope this helps! Good Luck!

Intersecting secant-tangent theorem states that if a tangent segment and a secant segment are drawn to a circle from an exterior point, then the square of the measure of the tangent segment is equal to the product of the measures of the secant segment and its external secant segment.so to break it down: 1. pq acts as the tangent and ps as the secant with an intersection at p.sr = 21rp = 3x + 3pq = 4x + 4following to equation: tangent squared = the two segments multiplied by each otherso (4x + 4) ^ 2 = (3x + 3) • (21) simplifies to 16x^2 - 31x - 47 = 0 or (16x - 47)(x + 1) x = -1 or x = 47/162. pq acts as the tangent and ps as the secant with an intersection at p (again! )sr = 16rp = xpq = 15(15) ^ 2 = 16 • x225 = 16xx = 225/163. the interesting chords are proportional to each other so a ratio is possible to set up: ap dp 10 3 + x = = —— = pc pb 8 xcross multiple to get 10x = (3 + x)(8)x = 12