181k views
1 vote
4x + y = 27 3x - y = 15

1 Answer

3 votes

Answer:

x = 6; y = 3

Explanation:

I would believe this is simultaneous equation

4x + y = 27 is equation 1

3x - y = 15 is equation 2

I’ll use substitution

Substitution :

In equation 1 let’s make either 4x or y the subject of the formula

I’ll use y

y = 27 - 4x let’s make it equation 3

4x because -4x because it went to the other side

Then we input the equation 3 into equation 2

So we replace y with equation 3

In equation 2 the coefficient of -y is 1 because we only have

one unit of y

3x - 1 (27 - 4x) = 15

Note : + x + = +

+ x - = -

- x - = +

- x + = -

That would make it be

3x - 27 + 4x = 15

We take like terms and move -27 to the other side

3x + 4x = 15 + 27

7x = 42

Divide both sides by the coefficient of x which is 7

x = 42/7

x = 6

To get why we input the answer for x in equation 3

y = 27 - 4(6)

y = 27 - 24

y = 3

To confirm we input the values in any of the equation

4(6) + 1(3)= 27

24 + 3 = 27

27 = 27

If you want me to use elimination just reply
happy helping :)

User James Cadd
by
8.3k points