The sum of two numbers is 45, and the larger number is 3 more than the smaller number. What is the smaller number?

24

21

18

21

Step-by-step explanation:

I set up a system of equations firstly.

x + y = 45

x = y + 3

After that, I substituted the equation I made for x into the parent equation, which simplified is 2y + 3 = 45.

Then, I subtracted the 3, then divided the result of 42 by 2, which gave me 21.