When adding and subtracting fractions of mixed denominators you will need to find the LCD (Least Common Denominator).
Example: 2/5 – 1/3 = 1/15. How I got there was I found the LCD by multiplying the denominators until they had the same denominator, then I multiplied the numerators by the same number it’s denominator was multiplied by, then I subtracted.
To multiply a fraction you do not find an LCD, and you just multiply it.
Example: 6/7 * 3/5 = 18/35. How I got that answer was I just multiplied 6 by 3, and 7 by 5.
Like multiplying fractions, you do not need find an LCD at all, but dividing fractions are different from multiplying fractions.
Example: 2/3 / 4/5 = 1 and 1/5. How I was able to get that answer was I flipped one of the numbers, and then multiplied and I got 12/10, but it was an improper fraction, so I subtracted 12-10 and I got 2/10, then I put a whole number, then I simplified the answer and got 1 and 1/5.