Answer :
Answer:
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.