Answer :
[tex]Amount\ of\ round\ balloons:\\6\cdot24=144\\\\Amount\ of\ long\ balloons:\\3\cdot36=108\\\\144-108=36\\\\The\ clown\ bought\ 36\ more\ round\ than\ long\ balloons.[/tex]
6 x 24 = 144 round balloons
3 x 36 = 108 long balloons
The clown has more round balloons than long balloons, so there is some misunderstanding in the question.