Question

the length of a rectangle is three times the width. the perimeter is 49 units.find the length

Answer 1

Let's say:
a = length
b = width
length = 3 x width
a = 3b
perimeter = 2 x ( a + b )
49 = 2 x ( 3b + b ) = 2 x 4b = 8b
b = 6.125
a = 3b = 3 x 6.125 = 18.375 unit

The length is 18.375 unit.

Answer 2

does 2 x(a+b) mean 2(a+b)