Rearrange the 2nd equation 
-36a-24b-16c
divide the whole thing by 4 and you'll get
-9a-6b-4c 
you'll realize it looks the same as your first equation except that all the + has become minus so the answer will be -7 instead for your new equation 
-9a-6b-4c=-7
multiply the whole thing by 4 and you'll get
-36a-24b-16c = -28
so the answer you want is -28
        
             
        
        
        
The exact form is:
-37/10
The decimal for is:
-3.7
The mixed number for is:
-3 7/10
        
             
        
        
        
N - the number
8/100 × n = 0.08 × n = 0.08n
        
                    
             
        
        
        
1’11”
Explanation:
12in in a ft so 24in = 2ft, but 23in only is 1ft 11in
Ft = ‘
In = “
Hope this helps!