Answer:
Rectangle: 27
Triangle: 39
Explanation:
To find the perimeter of a rectangle use the expression P = 2(l + w)
Before substituting 4.5 for x simplify the equation
2((-3 + x) + 1/2(4x + 6)) = P
First simplify in the parenthesis
2(-3 + x + 2x + 3) = P
Now combine like terms, then multiply 2 and 3x
2(3x) = P
P = 6x
Lastly substitute 4.5 for x to find the perimeter
P = 6(4.5)
P = 27
Now do the same thing that we did with the rectangle but with a triangle
P = a + b + c
(3x - 4) + (3x - 4) + 2/3(6x + 3) = P
10x - 6 = P
10(4.5) - 6 = P
P = 39