18=a over 2 how do you solve that as a one step

"a" is being divided by 2.
You want a alone, not divided by 2.
The operation that is opposite to division is multiplication.
Multiplication undoes division.
Multiply a/2 by 2 to get a.
A rule of equations is that you must do the same operation to both sides of the equation, so you must multiply both sides by 2.

18 = a/2

18 * 2 = a/2 * 2

36 = a

a = 36

Whose mistake? can you give more details to what the question is asking?

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