Question

−3x − 8y = 20 −5x + y = 19 solved by substitution

Answer 1

x=-4

y=-1

Explanation:

-3x-8y=20

-5x+y=19

rewrite for y:

y=19+5x

substitute y

-3x-8(19+5x)=20

-3x-152-40x=20

-3x-152-40x+152=20+152

-43x=172

-43x/-43=172/-43

x=-4

substitute x

-5(-4)+y=19

20+y=19

y=-1

check:

-3(-4)-8(-1)=20

12+8=20

-5(-4)+-1=19

20-1=19

Answer 2

Delete as this is the wrong answer. Made a typo in the answer.

Answer:

x =
`(-212)/(3)`

y = 24

Explanation:

-3x - 8y = 20 .... (1)

-5x + y = 19 .... (2)

What we can do is take the (2) equation

-5x + y = 19

and solve for y by adding 5x to both sides

y = 24

now that we have y we substitute it in for y in equation (1)

-3x - 8(24) = 20

-3x - 192 = 20

we want to solve for x so we need to get its self.

add 192 to both sides

-3x = 212

now we divide both sides by -3. It's going to be a fraction.

x =
`(-212)/(3)`