Do a proportion
60/100= x/54
Cross multiply and divide
54 x 60= 3,240
3,240 divided by 100 is 32.4
Now subtract
54- 32.4= 21.6
Answer is $21.6
The question reminds you of all the tools you need:
It says ...
"Opposite angles are equal."
So the upper right angle is x+40 just like the bottom left,
and the bottom right angle is 3x+20 just like the upper left.
And it says ...
"The sum of all angles is 360°."
You know what each of the four angles is, so you can addum all up,
set the sum equal to 360, find out what number ' x ' is, and then
use that to find the size of every angle.
6 : 2/3.....multiply by 3
18 : 2...reduce
9:1 or 9/1