There are many ways to do this depending on the property you have to use:
If you use the distributive property, you need to distribute 3/4 to -10 and 2/5. Distribute means you will multiply it so your resulting equation will be this:
[tex] \frac{-30}{4} - \frac{6}{20} [/tex]
Before you can add, you need to first make them like terms because you cannot add unlike fractions. Get the LCD and form your new equation:
[tex] \frac{-150+6}{20} [/tex]
Now you can just add them together to get: [tex] \frac{-144}{20} [/tex]
and then simplify your fraction: [tex] \frac{-36}{5} [/tex] or - [tex] \frac{36}{5} [/tex]
The whole fraction becomes negative because when you divide integers and of them is negative, the final answer will be negative.