How can you subtract mixed numbers when the fraction in the first mixed number is less tan the fraction in the second mixed number

You have to convert both mixed numbers into improper fractions, and then subtract. You convert by multiplying the denominator in the fraction by the whole number and then by adding the numerator to the product.

To subtract mixed numbers first convert the numbers to improper fractions. For example:

3 and 1/2 - 6 and 2/3 would be converted to 7/2 - 20/3

(The easiest way to convert these would be to multiply the whole number by the denominator of the fraction and then add the numerator eg; 6 and 2/3. 6 times 3 is 18, then add the 2. This makes 20. Then put this number over the initial denominator and hence, you get 20/3)

From this conversion of 7/2-20/3 you must make the denominators of both fractions the same. This is done by finding a common number that both the denominators can be divided into. In this case i would simply multiply the denominators by eachother to get 6. this means that the denominator (2) must be multiplied by 3 to get a denominator of 6, so the numerator must do the same and be multipled by 3. This leaves you with 21/6. The other improper fraction (20/3) must be multiplied by 2 to get the denominator of 6, so the numerator must do the same. This leaves you with 40/6. The sum is then 21/6-40/6. This is then simply done by minusing the numerators. so 21-40 leaves you with - 19. So your answer would be - 19/6.