# math/algebra

posted by
**Diana**
.

solve each of the following systems by substitution.

16) 5x -2y = -5

y - 5x = 3

20) 8x -4y = 16

y = 2x - 4

28) 4x -12y = 5

-x + 3y = -1

Step one: Solve on of the equations for one of the variables.

y=2x-4

Step two:Substitute the expression for the variable found in step one into the other equation.

8x-4(2x-4)=16

Step three:Solve the equation from step two to find the value of one variable.

Use the distributive property

8x-4(2x-4)=16

8x-8x+16=16

x+16=16

-16 -16

x=0

Step four:Substitute the value found in step three in any equation containing both variables to find the value of the other variable.

y=2x-4

y=2(0)-4

y=0-4

y=-4

step five: check the proposed solution in the orginal system.

8(0)-4(-4)=16

0+16=16

16=16

The equation is equal, so it is correct.

#28

4x-12y=5 -x+3y=-1

+x +x

3y=-x or -3y=x

4(-3y)-12y=5 4x-12(5)=5

-12y-12y=5 4x-60=5

y=5 +60 +60

4x=65

x=65/4

4(65/4)-12(5)=5

260/4 - 60=5

65 - 60 = 5

5 = 5

it's correct

I hope I helped