Step-by-step explanation:
1).
2x + 8y = 12 ......... Equation 1
x - 2y = 0 .............. Equation 2
Make x the subject in equation 2 and substitute it into equation 1
That's
x = 2y
We have
2(2y) + 8y = 12
4y + 8y = 12
12y = 12
Divide both sides by 12
y = 1
Substitute y = 1 into x = 2y
That's
x = 2(1)
x = 2
The answers are
x = 2 , y = 1
2.)
x + y = 7......... Equation 1
2x + y = 5 ......... Equation 2
Make y the subject in equation 1 and substitute it into equation 2
We have
y = x - 7
2x + x - 7 = 5
3x = 7 + 5
3x = 12
Divide both sides by 3
x = 4
Substitute x = 4 into y = x - 7
y = 4 - 7
y = - 3
We have the answers as
x = 4 , y = - 3
3).
y = -1/2 + 1 ......... Equation 1
2x + 3y = 6 ........ Equation 2
From equation 1
y = 1/2
Substitute y = 1/2 into Equation 2
So we have
2x + 3(1/2) = 6
2x + 3/2 = 6
2x = 6 - 3/2
2x = 9/2
Divide both sides by 2
x = 9/4
The answers are
x = 9/4 , y = 1/2
4).
2x - 1/3y = - 9.......... Equation 1
-3x + y = 15 ........... Equation 2
Make y the subject in equation 2 and substitute it into equation 1
That's
y = 15 + 3x
2x - 1/3( 15 + 3x) = - 9
2x - 5 - x = - 9
x = - 9 + 5
x = - 4
Substitute x = - 4 into y = 15 + 3x
That's
y = 15 + 3(-4)
y = 15 - 12
y = 3
The answers are
x = - 4 , y = 3
Hope this helps you
