Math need by 9pm cst
posted by SAP on .
Solve by elimination method. Please show step by step process.
7r4s=7
4r+7s=61

multiply the top equation by 7, and the bottome equation by 4.
Then add the equations, which will eliminate the s variable.
I will be happy to critique your work 
7r4s=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?