A. 68 cm
Step-by-step explanation
Rectangles have 2 pairs of parallel sides, so you should multiply both sides by two.
(8•2)+(9•2)=34
Since rectangle a perimeter is two times that of rectangle b perimeter, then you should find the perimeter of rectangle b and multiply it by two.
34•2=68
So the perimeter of rectangle a is 68cm.