If the  perimeter of a triangle is 19 cm. The lengths of 3 sides is: a = 8, b = 7, c = 4.
<h3>Parimeter</h3>
Let a = longest
Let b= shortest
Let c= third side
a = 2c
a = (b+ c) - 3
a + 3 = b + c
Using three variables to solve the expression for perimeter 
Perimeter= 19 cm
a+ b + c = 19
a + (a + 3) = 19
2a + 3 = 19
2a= 16
Divide both side by 2a
a=16/2
a = 8
a = 2c 
8 = 2c  
c=8/2
c = 4
a + b + c= 19
8 + b + 4 = 19
12 + b = 19
b=19-12
b = 7
Hence,
a = 8, b = 7, c = 4
Therefore If the  perimeter of a triangle is 19 cm. The lengths of 3 sides is: a = 8, b = 7, c = 4.
The complete question is:
Perimeter of triangle is 19cm. If the length of the longest side is twice that of the shortest side and 3 less than the sum of the lengths of the 2 sides find lengths of 3 sides.
Learn more about perimeter here:brainly.com/question/19819849
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What is the number line?
If you answer i could help you even more with the answer
        
             
        
        
        
Answer:
Step-by-step explanation:
5h-8=2h+19
5h-2h=19+8
3h=27
h=27/3
h=9
 
        
             
        
        
        
263.27 m^2
rectangle : 15 x 10 = 150 m^2
the half circle at the top has a diameter of 6m. therefore, it’s radius is 3m. if it is cut in half, the part removed from the triangle height is 3m. therefore, the height of the triangle is 35 -15 = 20; 20 - 3 = 17. the height of the triangle is 17. the triangle area formula is a = 1/2(bh). 
a = 1/2 (10)(17)
a = 1/2 (170)
a = 85 m^2
the circle would be a = πr^2 but divided by 2 bc it’s a half circle 
a = π(3)^2
a = π9
a = 28.27 m^2
150 + 85 + 28.27 = 263.27 m^2