Question 37378
Drawing a red marble the chance is 6/10. After replacement of the red marble the chance of drawing a blue is 4/10. Since these are independent events you derive the result of both drawing the red marble and then drawing a blue marble by multiplying the two probabilies. Hence, the answer is 
6/10 x 4/10 = 24/100 = 6/25 = 24%.

Hope this helps 

Sincerely,
BlimBlim (the wizard)