It takes joey 1/6 of an hour write one you card. how many cards can he write in 3/4 of an hour?

1/6 of an hour is equivalent to 10/60 or 10 minutes.
To find out how much 3/4 of an hour is, change the denominator of both fraction so that they match up. We can make this easier by multiplying 4 by 15 to get 60 (hence an hour) and since we multiplied 4 by 15, we also need to multiply 3 by 15 which gets us 45.
We end up with 10/60 and 45/60 or 10 minutes and 45 minutes.
Half of 10 is 5 so we know we'll have a decimal of .5 in our answer.
4 times 10 equals 40 and 40 plus 5 equals 45, so 4.5.

0.61 has 2 decimal places, so we put the decimal digits of 0.61, 61 over 1 followed by the number of zeroes equal to the number of decimal places, 

2:     61/1 = 61/100.

0.61 as  decimal fraction  = 61/100