it says solve by elimination..
2007-09-15 11:22:55 · 7 answers · asked by Sam 1 in Science & Mathematics ➔ Mathematics
7x + 15y = 32
-7( x - 3y = 20)
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7x + 15y = 32
-7x + 21y = -140
Add them together vertically
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0x + 36y = -108
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y = -3
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Now place -3 in place of "y" in one of your equasions
x - 3(-3) = 20
x + 9 = 20
x = 11
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Answer:
x = 11
y = -3
2007-09-15 11:31:30 · answer #1 · answered by Kyle R 2 · 1⤊ 0⤋
Multiply 2nd equation by 7 and subtract from the 1st.
You eliminate x and you get y(15+21) = (32-140)
or 36y = -108 or y =-108/36 = -27/9 = -3
Substitute in equation #2 and you get
x -(3x-3) = 20 or x+9 = 20 or x=11.
2007-09-15 11:36:35 · answer #2 · answered by stvenryn 4 · 0⤊ 0⤋
7x+15y=32
x-3y=20
multiply the second guy by five and add to the first
12x = 132
x = 11
(11)-3y = 20
-3y = 9
y = -3
2007-09-15 11:28:26 · answer #3 · answered by PMP 5 · 0⤊ 0⤋
7x+15y=32----------------(1)
& x-3y=20------------------(2)
multiplying (2) by 5 ,we have
5x-15y=100----------------(3)
adding (1) & (3)we get
12x=132
or x=11,putting this value in (2)we get
11-3y=20 or -3y=20-11=9 or y=-3 ans
2007-09-15 11:33:41 · answer #4 · answered by MAHAANIM07 4 · 0⤊ 0⤋
x = 20 + 3y . . . . substitute to the other equation
7(20 + 3y ) + 25 y = 32
140 + 21 y + 25 y = 32
46 y = - 108
y = - 54 / 23
2007-09-15 11:41:15 · answer #5 · answered by CPUcate 6 · 0⤊ 0⤋
multiply the second by 5
5x - 15y = 100
add
12x = 132
x = 11; y = -3
2007-09-15 11:30:48 · answer #6 · answered by Beardo 7 · 0⤊ 0⤋
are you solving for x or y?
2007-09-15 11:28:27 · answer #7 · answered by Tim S 2 · 0⤊ 0⤋