Answer:
length = 20
Width = 14
Step-by-step explanation:
x - y = 6 Â -------------------(I)
x + y = 34 ------------------(II)
Add equation (I) & (II). So y will be eliminated and you can find the value of x
(I) Â Â Â Â x - y = 6
(II) Â Â Â x + y = 34 Â {Now add}
    2x    =  40    {Divide both sides by 2}
       x  = 40/2
x = 20
Plugin x = 20 in equation(II)
20 +y = 34
    y = 34 -20
y = 14