Let f=first number, s=second number. Here's the translation:
"The difference (-) of two numbers(s and f) is (=) 45"
"The second (s) is (=) 3 less (-3) than 3 times the first(3f)"
So plug in into
Add like terms
Subtract 3 from both sides
This is our first number
So the 1st number is 24. Use this to find the second number:
Add 24 to both sides
This is our second number
So the 2 numbers are 69 and 24
Check:
Plug in f=24 and s=69
works
Plug in f=24 and s=69
works