First, convert both of them to improper fractions:
-4 1/5
1. Multiply the whole number (4) by the denominator (5) to get 20 (ignore - signs for now)
2. Add the numerator (1) to get 21
3. Put it over the denominator to get 21/5. Now add a minus sign to get $${\mathtt{\,-\,}}{\frac{{\mathtt{21}}}{{\mathtt{5}}}}$$
Do the same for the other fraction to get $${\mathtt{\,-\,}}{\frac{{\mathtt{10}}}{{\mathtt{3}}}}$$
Now find the Least Common Multiple (LCM) for the denominators, 3 and 5. Keep multiplying 5 until you get a number that works for both 3 and 5. In this case, it is 15. 3*5=15 and 5*3=15. Multiply them by those numbers so that the denominator is 15:
$${\mathtt{\,-\,}}{\frac{{\mathtt{21}}}{{\mathtt{5}}}}$$ X $${\frac{{\mathtt{3}}}{{\mathtt{3}}}}$$ = $${\mathtt{\,-\,}}{\frac{{\mathtt{63}}}{{\mathtt{15}}}}$$
Do the same for $${\mathtt{\,-\,}}{\frac{{\mathtt{10}}}{{\mathtt{3}}}}$$, but multiply by 5/5 instead of 3/3. This will give you $${\mathtt{\,-\,}}{\frac{{\mathtt{50}}}{{\mathtt{15}}}}$$. Now that they both have the same denominator, you can multiply them together.
$${\mathtt{\,-\,}}{\frac{{\mathtt{50}}}{{\mathtt{15}}}}$$ X $${\mathtt{\,-\,}}{\frac{{\mathtt{63}}}{{\mathtt{15}}}}$$
Cross reduce if you're in the mood, but to keep things short I'll skip it.
-50*-63=3150 (remember that negative*negative=positive)
Leave the denominators alone.
This gives you $${\frac{{\mathtt{3\,150}}}{{\mathtt{15}}}}$$. You can then simplify it. 3150 is divisible by 15, so you can divide to get $${\frac{{\mathtt{210}}}{{\mathtt{1}}}}$$, or just plain 210.
Good luck.