7r-4s=-7 (7)

4r+7s=61 (4)

49r - 28s = -49
16r + 28s = 244
---------------
65r = 195
195/65 = 3 (simplified) (3, is the first number of the ordered pair.)

Now this is the part that I get lost on. I know I am suppose to substitute 3 into one of the equations above, but how do I determine which one. So if I substitute 3 into the 1st equation:

7(3)-4s= -7
21 - 4s= -7
------------
21 = -7 would my answer be -7/21

Substitute 3 into the 2nd equation:

4(3)+7s = 61
12 + 7s = 61
-------------
12 = 61 would my answer be 61/12

(3, is the first number of the ordered pair.)

(3,-7/21) or (3,61/12) which ordered pair is correct?

To determine which equation to substitute the value of 3 into, you can choose either equation. The important thing is that once you substitute the value, you should get a true statement. In this case, you can substitute 3 into both equations and check which one gives you a true statement.

Let's substitute 3 into the first equation:

7(3) - 4s = -7
21 - 4s = -7
Subtract 21 from both sides:
-4s = -7 - 21
-4s = -28
Divide both sides by -4:
s = -28 / (-4)
s = 7

Now let's substitute 3 into the second equation:

4(3) + 7s = 61
12 + 7s = 61
Subtract 12 from both sides:
7s = 61 - 12
7s = 49
Divide both sides by 7:
s = 49 / 7
s = 7

In both cases, substituting 3 into both equations gives you the value of s as 7. Therefore, the correct ordered pair is (3, 7).

Note that when you were checking your work, it seems like there was a mistake in your calculations. In the first equation, the correct result after substituting 3 should be s = 7 (not -7/21), and in the second equation, the correct result after substituting 3 should be s = 7 (not 61/12).