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Question
Solve the pair of linear (simultaneous) equations by the method of elimination by substitution:
8x + 5y = 9
3x + 2y = 4
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Solution
8x + 5y = 9 ...(1)
3x + 2y = 4 ...(2)
8x + 5y = 9
8x = 9 − 5y
`x = (9 - 5y)/8` ...(3)
3x + 2y = 4
Putting x = `(9 - 5y)/8`
`3x ((9 - 5y)/8)` + 2y = 4
`(27 - 15y) /8 + 2y = 4`
`(27 - 15y + 16y)/8 = 4`
`(27 + y)/8 = 4`
27 + y = 32
y = 32 − 27
y = 5
Putting y = 5 in questions (3)
`x = (9 - 5 xx 5)/8`
`x = (9 - 25) /8`
= `-16/8`
x = −2
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