First thing to do is set up your equation:
45/x = 20/100
Cross multiply
4500 = 20x
And divide by 20
Answer: 225 people were surveyed
I would say 12 hours and 38 min
70% is the same as 70/100 then we simplify by taking off one zero of each number 7/10 and we can't divide it any more so the answer is 7/10
