36 ft 24 ft 11 ft 11 ft

Your answer is : (2') now subtract eq(2') from eq(1'). the terms "6y" will cancel each other, and you will get a single equation for  only one  unknown x: (it is  how  the elimination method works). 9x - 8x = 54 - 50 > x = 4. thus we  just  found that  one  birthday card costs 4 dollars.  then  from eq(1) 3*4 + 2y = 18 > 2y = 18 - 12 = 6 > y  .hoped this : )