You made this very confusing could you post clearer picture
Answer:
$14.4
Step-by-step
c = x + 0.07x + 0.18x
18 = x + 0.07x + 0.18x
18 = 1.25x (simplify)
14.4 = x (divide both sides by 1.25)
X+(4x-20)=180
=>5x-20=180
=>5x=200
=>x=40
Well, there's:
7 * 2 =14
and
7 * 3 = 21
Both of these have only the factor 7 in common. Therefore, it is the greatest factor. You can use any combination of numbers that have a factor of 7 and only 7 in common.