(5b/2y)(-3y/10b^2)

wouldn't that just be

-3/(4b) ?

can you explain how you got there?

To multiply the given fractions, you can follow these steps:

Step 1: Multiply the numerators (the numbers on the top) together.

In this case, the numerators are 5b and -3y. Multiply them together:
5b * -3y = -15by

Step 2: Multiply the denominators (the numbers on the bottom) together.

In this case, the denominators are 2y and 10b^2. Multiply them together:
2y * 10b^2 = 20by^2

Step 3: Write the resulting product of the numerator and the product of the denominator as a new fraction.

Combining the results from steps 1 and 2, the new fraction is:
(-15by) / (20by^2)

Step 4: Simplify the fraction, if possible.

In this case, the variables b and y can be canceled out since they appear in both the numerator and denominator. So, you can divide them cancel out:
(-15by) / (20by^2) = (-15/20) * (1/y) = (-3/4) * (1/y) = -3/4y

Therefore, the result of the given expression (5b/2y)(-3y/10b^2) is -3/4y.