Question

7 relationships continued (7x - 21)° (9x + 1)° 8

Explanation:

Step1: Identify angle - relationship

The two angles $(7x - 21)^{\circ}$ and $(9x + 1)^{\circ}$ are supplementary (linear - pair of angles, sum to 180°).
$7x-21 + 9x + 1=180$

Step2: Combine like - terms

Combine the $x$ terms and the constant terms on the left - hand side of the equation.
$(7x+9x)+(-21 + 1)=180$
$16x-20 = 180$

Step3: Isolate the variable term

Add 20 to both sides of the equation.
$16x-20+20=180 + 20$
$16x=200$

Step4: Solve for $x$

Divide both sides of the equation by 16.
$x=\frac{200}{16}=\frac{25}{2}=12.5$

Answer:

$x = 12.5$