Respuesta :

Answer:

112 cm (red, 4)

Step-by-step explanation:

length = b

width = a

b = 7a

42 = b - a

42 = 7a - a

42 = 6a

a = 7          => b = 7a       b = 7*7 = 49

Perimeter = 2*(a+b)

= 2*(7+49)

= 2*(56)

= 112 cm