He sold 12 smartphones along with 20 accessories.
Answer:
Step1: Take away (cx+d) from both sides of the initial equation
Thus, the value of x from the equation is 
Detailed explanation:
Considering the equation a-bx=cx+d
To find x:
a-bx=cx+d
Step1: Remove (cx+d) on both sides of the initial equation
a-bx-(cx+d)=cx+d-(cx+d)
a-bx-cx-d=cx+d-cx-d
a-bx-cx-d=0
Rearranging this yields
a-b-bx-cx=0
(a-b)-x(b+c)=0 (combining similar terms)
-x(b+c)=-(a-d)
Thus, the value of x in the initial equation is 
An estimate of approximately 2/3 meters would be sensible.
In order to solve this, we will use proportions. The first step involves converting centimeters to meters by applying dimensional analysis:


Once everything is expressed in meters, we can set up the proportions accordingly. Our proportion becomes 
First, we perform cross-multiplication: 
Then, by dividing both sides by 0.59, we arrive at x = 18.6 m, or D.