Find a number you can multiply by the bottom of the fraction to make it 10, or 100, or 1000, or any 1 followed by 0s.
Multiply both top and bottom by that number.
Then write down just the top number, putting the decimal point in the correct spot (one space from the right hand side for every zero in the bottom number)
Since there are 12 inches in 1 foot you have to divide 84 by 12
84 divided by 12 is 7
So, there are 7 feet in 84 inches
For 1 hour, money = $20
For $140, it would be: 140/20 = 7 hours.
So, option C is your final answer.
Hope this helps!
