Question

7x+2y=3 and x-3y=30, what is the value of y?

Answer 1

Answer:

y = -9

x = 3

Step-by-step explanation:

in order to determine the value of y in the equation we would say let

7x+2y=3 .......................................... equation 1

x-3y=30.......................................... equation 2

from equation 2

x-3y=30.......................................... equation

x = 30 + 3y..................................... equation 3

substitute for equation 3 into equation 1

7x+2y=3 .......................................... equation 1

7( 30 + 3y) + 2y = 3

210 + 21y + 2y = 3

210 + 23y = 3

combine the like terms

23y = 3 - 210

23y = - 207

divide both sides by the coefficient of y

23y/23 = -207/23

y = -9

substitute for y =-9 into equation 3

x = 30 + 3y..................................... equation 3

x = 30 + 3(-9)

x = 30 -27

x = 3

Answer 2

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I'm solving it using substitution method:-

7x+2y=3 {given}

=>7x=3-2y

=>x=(3-2y)/7-------(1)

x-3y=30 {given}

=>x=30+3y

=>(3-2y)/7=30+3y {putting the value of x from eqn 1}

=>3-2y=210+21y

=>3-210=21y+2y

=>-207=23y

=>y= -207/23= -9

putting the value of y on eqn(1):-

x=(3-2y)/7

x=>(3-2(-9))/7=(3+18)/7=21/7=3

Hence, x=3, y= -9

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