If 100 km are equal to 62 miles then your ratio would look like 100:62.
Now you would like to figure out how many km are equal to 75 miles.
Your ratio would look like k:75.
75 divided by 62 is 1.20967742... which you can round to 1.21
Now multiply the 100 km by 1.21.
By doing this, you get 121.
So, 121 km is equal to 75 miles.