Question

What is the value of x + y in the solution to the system of equations below?

x + 8y = 2
y = -0.25x

I just need the best explanation so i can do all my other problems cause im confused.

Answer 1

multiply the second equation by 4
4y=-x or x+4y=0

so now you have
x+8y=2
x+4y=0
subtract the second equation from the first.
4y=2
y=1/2 then solve for x
x+4y=0 or x=-2

Answer 2

With substitution:

x + 8(-.025x) = 2
x + -.2x = 2
.8x = 2
x = 2/.8 = 2.5

Answer 3

x + 8y = 2
y = -0.25x

Substitute.

x + 8(-0.25x) = 2

x - 2 = 2

x = 4

Answer 4

Wow: three answers. Edgard, recommend you do some checking of the answers, that checking will teach you some algebra.
Ms Sue, yours should read:
x-2x=2
x=-2
Dr M: you didn't multipy .25 correctly...

Answer 5

Thanks, Bobpursley. I goofed!