Hello, I need did a subtraction problem with mixed numbers by converting the LCD of the denominator.

However, when I went to Algebra.help they did the problem by converting the mixed problem to an improper fraction and then worked it that way.

However, I know that the answers should be the same.

Please check my method. I don't want to convert the whole numbers to mixed.

9 10/12 minus 5 6/7
9 70/84 minus 5 72/84
equals 4 2/84
reduced to 4 1/42

Algebra help say the answer is:
3 41/42

4 answers

Your algebra help is correct.

Your problem is in your second step. You can't take 72 from 70. Therefore, you need to change 9 70/84 to 8 154/84.

8 154/84 - 5 72/84 = 3 82/84 = 3 41/42
How did you change 9 70/84 to 8 154/84?
Subtract 1 frp, 9 and add to the fraction.

1 = 84/84
23/6 convert to a mix number