Okay. Let's make a proportion for this. So we can do 21/3=x/60. Let's multiply cross way. So 21 x 60 is 1260. We multiply 3 by x to get 3x. So our equation will be 3x=1260. We can isolate the equation by 3, and 1260 divided by 3 is 420. So x=420. We then have to convert into feet. So 420 divided by 12 is 35. So it would be 35 feet. Therefore, the machine can make 35feet of ribbon in a hour.
