1. Solve for x: 5:25 = 7:x
2. Solve for x: 8/x = 12/(x + 2)
3.Solve for x: 12/21 = (x - 5)/x
4. Solve for x: 7/12 = x/15
2007-11-27 04:10:59 · 10 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
1)5:25 = 7:x
5x=7*25
x=7*25/5
x=7*5
x=35
2)8/x=12/(x+2)
8*(x+2)=12*x
8x+16=12x
16=12x-8x
16=4x
16/4=x
4=x
3)12/21 = (x - 5)/x
12*x=21*(x-5)
12x=21x-105
12x-21x=-105
-9x=-105
9x=105
x=11.67
4)7/12 = x/15
7/12*15 = x
7/4*5=x
35/4=x
8.75=x
2007-11-27 04:18:44 · answer #1 · answered by Siva 5 · 0⤊ 1⤋
1. 5/25 = 7/x
=> 1/5 = 7/x
x = 7 . 5
x = 35
2. 8/x = 12/(x+2)
8 (x+2) = 12x
8x + 16 = 12x
16 = 12x - 8x
16 = 4x
16/4 = x
4 = x
3. 12/21 = (x-5)/x
12x = (x-5)21
12x = 21x - 105
105 = 21x - 12x
105 = 9x
105/9 = x
35/3 = x
4. 7/12 = x/15
7 . 15 = 12x
105 = 12x
35/4 = x
2007-11-27 13:38:31 · answer #2 · answered by chocolate_gurl 2 · 0⤊ 0⤋
For each of these you can first cross-multiply
a/b = c/d
ad = bc
1. Solve for x: 5:25 = 7:x
Actually, you might first simplify when possible
1/5 = 7/x
x = 35 {cross-multiply}
2. Solve for x: 8/x = 12/(x + 2)
2/x = 3/(x + 2) {divide both sides by 4}
2(x + 2) = 3x {cross-multiply}
2x + 4 = 3x
-x = - 4
x = 4
3.Solve for x: 12/21 = (x - 5)/x
4/7 = (x - 5)/x
4x = 7(x - 5)
4x = 7x - 35
-3x = - 35
x = 35/3
4. Solve for x: 7/12 = x/15
7/4 = x/5
4x = 35
x = 35/4
2007-11-27 12:29:47 · answer #3 · answered by kindricko 7 · 0⤊ 0⤋
1. 5x = 25 x 7
5x = 375 (divide both sides by 5)
x = 75
2. 8/x = 12/(x+2)
8(x+2) = 12x
8x+16 = 12x
8x-12x = -16
-4x = -16
x = 4
3. 12/21 = (x-5)/x
12x = 21 (x-5)
12x = 21x-105
12x-21x = -105
-9x = -105
x = 105/9 or 35/3 or 11 and 2/3
4. 7/12 = x/15
7 x 15 = 12x
105 = 12x
x = 105/12 or 35/4 or 8 and 3/4
2007-11-27 12:21:41 · answer #4 · answered by ruby_alabar 3 · 0⤊ 1⤋
1) 5 * x = 25 * 7
5x = 175
x = 35
2) 8(x+2)= 12 * x
8x+16=12x
16=12x-8x
16=4x
x=4
3) 12x = 21(x - 5)
12x = 21x - 105
9x = 105
x = 11.67
4) 7*15 = x*12
105 = 12x
x = 8.75
2007-11-27 12:20:47 · answer #5 · answered by Anonymous · 0⤊ 0⤋
5*x = 7*25.
x = 7*25/5
x = 35.
2.
8/x = 12/(x + 2)
8(x+2) = 12x
8x + 16 = 12x
16 = 4x
x = 4.
3.
12/21 = x-5/x
12x = 21(x - 5)
12x = 21x - 105
0 = 9x - 105
105 = 9x
35 = 3x
x = 35/3
4.
7/12 = x/15
7*15 = x*12
7*5 = x*4
35 = 4*x
x = 35/4
2007-11-27 12:21:29 · answer #6 · answered by Edgar Greenberg 5 · 0⤊ 1⤋
Cross multiplication:
(1) 5x=175; x=35
(2) 8x+16=12x; x=4
(3) 12x=21x-105; x=35/3
(4) 105=12x; x=105/12
2007-11-27 12:17:16 · answer #7 · answered by someone2841 3 · 0⤊ 1⤋
Simple cross-multiplication should do the trick:
(1) 5x = 275
x = 55
(2) 12x = 8(x + 2)
12x = 8x + 16
4x = 16
x = 4
(3) 12x = 21(x - 5)
12x = 21x - 105
9x = 105
x = 11.67
(4) 12x = 105
x = 8.75
Hope I helped!
2007-11-27 12:17:53 · answer #8 · answered by Jacob F 5 · 0⤊ 1⤋
5:25 = 7:x
5x=175
x=35
answer to 1st one
2007-11-27 12:20:38 · answer #9 · answered by seanrw93 1 · 0⤊ 1⤋
1. x= 35
2. x= 4
3. x= -0.15
4. x= 8.75
2007-11-27 12:18:00 · answer #10 · answered by laulaukins 1 · 0⤊ 0⤋