1.

If 28x -5y=36and 15x+5y+18=68, whatis the value of x ?

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Solution :Stary by WRITING the second equatin in the same form as the first, then use combination to solve for x:
` 28x-5y=26`
`(+15 +5y=50)/({:(43x, ""=86),(x, ""=2 ):}`
Choice (B) is correct.
If you feel more comfortable USING substitution, you can maximize efficiency by solving one equation for 5y and substituting that VALUE into the other equation:
`15x + 5y =50`
`5y =50-15x`
`28x -(50-15x ) =36`
`43x -50 =36`
`43x =86`
`x =2`
Note that the arithmetic is fundamentally the same, but the setup using combination is quicker and visually easier to follow.


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