Two numbers sum to 56. thrice the first subtracted from the second is 4. find the numbers?
The two numbers are
There are two numbers. Let's call them
Thrice the first subtracted, so
Now you have a simultaneous equation to work with.
Same signs subtract, Different signs add. I always prefer dealing with the number after the operation, so I'll start with that. We should make the coefficients the same.
If we add the bottom to the top, we end up with
Substitute your answer for
Let's take the given one.