Respuesta :

Answer:

3.  3x^2 + 15x

4.  x=36

Step-by-step explanation:

The area of a rectangle is

A = l*w

A = (3x)*(x+5)

Distribute

3x^2 + 15x

2/3x - 4 = 20

Add 4 to each side

2/3x -4+4 = 20+4

2/3x = 24

Multiply each side by 3/2

2/3*3/2 =24*3/2

x = 12*3

x=36

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