To solve (-4/9)(7/5) you can multiply straight across (multiply the numerators and then the denominators), and you get (-28/45).
To help you choose your numerators, you need to find 2 or more numbers that multiply to make 28. Examples would be 4 and 7, 2 and 14, and 1 and 28.
You need to do the same for the denominators. Numbers that multiply to make 45 include 5 and 9, and 3 and 15.
Since multiplying fractions is simply multiplying the numbers in the top over the numbers is the bottom, you can make fractions with a combination of these numbers listed above. However, make sure you make one fraction negative.