You can set this up as 2 fractions equal to each other, like ratios.
18/11=108/x
Cross multiply and you get 18x=1,188
Now divide both sides by 18 and get x.
x=66.
If the height of the building is 108ft, the width is 66ft.
Answer:

Step-by-step explanation:
The given ratio is 
9 is the common factor of 18 and 27
divide numerator and denominator by 9

hence
is proportion with 
Answer:
x = 9.17 (nearest hundredth)
The variable x is the amount the student needs to save each month in addition to his usual saved amount of $20.
Step-by-step explanation:
350 = 12(x + 20)
Multiply out brackets: 350 = 12x + 240
Subtract 240 from both sides: 110 = 12x
Divide both sides by 12: 9 1/6 = x
x = 9.17 (nearest hundredth)
The variable x is the amount the student needs to save each month in addition to his usual saved amount of $20.
Multiply -12 to each of the terms (make sure to carry the negative!)
-36a - 24b + 12 will be your final answer :)