First, you want to make the denominator's the same so you find a common denominator. 9 times 2 equals 18 so 18 is your common denominator.Since you multiplied 9 times 2 you need to do the same to the numerator,so it's 10 over 18( 10/18). Then, you want to multiply 1 times 9 to get the numerator of 3 1/2 which gives you 9 over 18 ( 9/18). Now that the denominators are the same just subtract the numerators which gives you 1/18. Lastly you want to subtract the whole numbers.3 subtracted by 2 is 1 so your answer is 1 1/18