SOLUTION: 5r-4s= -6 and 4r+5s=69

Question 248015: 5r-4s= -6 and 4r+5s=69
Answer by oberobic(2304) (Show Source): You can put this solution on YOUR website!
5r - 4s = -6
4r + 5s = 69
.
Subtract the second equation from the first
.
r - 9s = -75
.
Add 9s to both sides.
r = 9s - 75
.
Substitute
.
4r + 5s = 69
4(9s - 75) + 5s = 69
36s - 300 + 5s = 69
.
Add 300 to both sides
36s + 5s = 300 + 69
.
Collect terms.
41s = 369
.
Divide both sides by 41.
s = 369/41 = 9
.
Substitute into the other equation.
4r + 5(9) = 69
4r + 45 = 69
.
Subtract 45 from both sides.
4r = 24
.
Divide both sides by 4.
r = 6
.
So, we have the candidate answer is:
s = 9
r = 6
.
Check by substituting the values into the original equations.
.
5r - 4s = -6
5r = 30
4s = 36
5r - 4s = -6
OK
.
4r + 5s = 69
4r = 24
5s = 45
4r + 5s = 69
OK
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