Evaluating Equations

Question

Find the value of y for the given value of x.

1)3x-4y=7;x=5

2)-2x+y=-3;x=-1

3)-x+3y=-3;x=6

4)6x-5y=44;x=4

5)7x+5y=15;x=5

Answer 1

1) The equation 3x-4y=7

x=5

The x value substitute in above equation

3(5)-4y=7                                                (Multiply:3*5=15)

15-4y=7

Subtract 15 from each side

15-4y-15=7-15                          (Subtract:7-15=-8)

-4y=-8

Divide each side by -4

-4y/-4=-8/-4                              (Divide:-8/-4=2)

y=2

The value of y is 2.

2) -2x+y=-3;x=-1

The equation -2x+y=-3

x=-1

The x value substitute in above equation

-2(-1)+y=-3                               (Multiply:-2×-1=2)

2+y=7

Subtract 2 from each side

2+y -2=-3-2                              (Subtract:-3-2=-5)

y=-5

The value of y is -5.

3) -x+3y=-3;x=6

The equation -x+3y = -3

x = 6

substitute x = 6 in above equation

-6+3y = -3                                 

-6+3y+6 = -3+6                       (Add 6 to each side)                       

3y = 3                                     (Add:-3+6 = 3)

3y/3 = 3/3                               (Divide each side by 3)

y = 1                                       (Simplify)

Solution:

The value of y = 1

4) 6x-5y=44;x=4 The equation 6x-5y=44;x=4 x=4 The x value substitute in above equation 6(4)-5y=44                             (Multiply:6*4=24) 24-5y=44 Subtract 24 from each side 24-5y-24=44-24                     (Subtract:44-24=20) -5y=20 Divide each side by -5 -5y/-5=20/-5                           (Divide:20/-5=-4) y = -4 The value of y is -4 5) 7x+5y=15;  x=5 The x value substitute in above equation 7(5)+5y=15                          (Multiply:7*5=35) 35+5y=15 Subtract 35 from each side 35-35+5y=15-35                 (Subtract:15-35=-20) 5y=-20 Divide each side by 5 5y/5=-20/5                         (Divide:-20/5=-4) y=-4 The value of y is -4

 

Answer 2

1) Given eqation are

3x -4y  = 7, x = 5

Substitute the x value in 3x-4y = 7

3(5)-4y = 7

15-4y = 7

Subtract 15 from each side.

15- 4y-15 = 7-15

- 4y  = - 8

Divide each sides by negitive 4.

-4y/-4 = -8/-4

⇒  y = 2

Answer 3

2) Given eqation is -2x+y = 3, x = -1

Substitute the x value in eqution

      -2(-1) + y = 3

      2+y  = 3

Subtract each sides with 2

         2-2+y = 3-2

       ⇒ y = 1

3)-x+3y   = -3, x = 6

Substitute the value of x in eqation

      -6+3y  = -3

Add each sides 6

       6-6+3y = -3+6

        3y  = 3

Divide each sides with 3

        3y/3 = 3/3

        ⇒ y =  1

4)Given equation is

6x-5y = 44,x = 4

Substitute the value of x in eqation

      6(4) -5y  = 44

       24-5y  = 44

Subtract  24  each sides

       24-24-5y = 44-24

     -5y  = 20

Divide each sides with 5

      -5y/5  = 20/5

       -y = 4

       ⇒ y = -4

5)Given eqution is 7x+5y = 15,x = 5

Substitute the value of x in eqation

                     7(5)+5y = 15

                     35+5y  = 15

Subtract  35  each sides

                   35-35+5y = 15-35

                               5y = -20

Divide each sides with 5

           5y/5 = -20/5

          ⇒  y = -4