Answer:
x-3y
Explanation:
Distributive Property:
↓
A(B+C)=AB+AC
First, you multiply by the numbers or fractions from left to right.

1*5x-15y=5x-15y

5x-15y=5(x-3y)

Divide the numbers from left to right to find the answer.

x-3y is the correct answer.
I hope this helps you, and have a wonderful day!