Question

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3х - 4y = 15
7x+y= 4
Substitution

Answer 1

3x-4y=15

7x+y=4

Solve7x+y=4 for y:

7x+y=4

7x+y+−7x=4+−7x (Add -7x to both sides)

y=−7x+4

Step: Substitute −7x+4 for y in 3x−4y=15:

3x−4y=15

3x−4(−7x+4)=15

31x−16=15 (Simplify both sides of the equation)

31x−16+16=15+16 (Add 16 to both sides)

31x=31

(Divide both sides by 31)

x=1

Step: Substitute 1 for x in y=−7x+4:

y=−7x+4

y=(−7)(1)+4

y=−3(Simplify both sides of the equation)

Answer: x=1 and y=−3