r+6/5 = r+8/7
2007-09-10 08:44:33 · 4 answers · asked by . 1 in Science & Mathematics ➔ Mathematics
Cross Multiply...
7(r + 6) = 5(r + 8)
7r + 42 = 5r + 40
2r = -2
r = -1
2007-09-10 08:49:15 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Proportional problem
rewrite
(r + 6)/ 5 = (r + 8) / 7
The means : 5((r +8)
The extremes : 7(r + 6)
The equation
5(r + 8) = 7(r + 6)
The distributive property on the left and right side of the equation
5r + 40 = 7r + 42
Transpose 5r
5r + 40 - 5r = 7r + 42 - 42
Collect like terms
40 = 2r + 42
Transpose 42
40 - 42 = 2r + 42 - 42
Collect like terms
- 2 = 2r
Divide both sides of the equation by 2
- 2/2 = 2r/2
- 2/2 = r
- 1 = r
- - - - - - -s-
2007-09-10 16:06:10 · answer #2 · answered by SAMUEL D 7 · 0⤊ 1⤋
Sorry, first answerer is wrong.
I am GUESSING that you mean
(r+6)/5 = (r+8)/7. Cross multiply
7(r+6) = 5(r+8), distribute
7r + 42 = 5r + 40 (see the mistake in 1st answer?). gather like terms
7r - 5r = 40-42, note sign changes
2r = -2, divide by 2
r = -1.
2007-09-10 15:53:53 · answer #3 · answered by pbb1001 5 · 0⤊ 1⤋
something wrong with your equation, otherwise if you mean (r+6)/5 = (r+8)/7
then r = -1
2007-09-10 15:52:01 · answer #4 · answered by Quicksand 2 · 0⤊ 1⤋