5/4 is the constant of proportionality
        
             
        
        
        
Answer:
Length 37 cm, width 25 cm.
Step-by-step explanation:
Let the original dimensions be length x and width  x - 12 cms.
The new dimensions will be length (x - 2) and width (x - 12 - 2) = x-14 cm.
So , from the areas, we have:
x(x - 12) - (x - 2)(x - 14) = 120
x^2 - 12x  - (x^2 - 16x + 28) = 120
-12x + 16x - 28 = 120
4x = 148
x = 37 cms
So the length was 37 cm and the width was 37-12 = 25 cm.
 
        
             
        
        
        
I'd use the point-slope form, because it'd require the least amount of work.
The slope of this line is 3/1, or just 3.
Thus, y = mx + b  becomes  3 = 3(1) + b, and b = 0.  Thus, we get y = 3x (ans.)
        
             
        
        
        
3(5)-15+10(7)-2(5)
15-15+70-10
=60
The answer is 60