Algebra 1
posted by Kalleigh .
Substitution
x  5y=10
2x  10y=20

The equations are the same (divide the second equation by 2). There is no solution.

to do substitution: you choose one equation, then represent one of the variables in terms in terms of the other. and finally substitute it the the other equation.
(1) x  5y = 10
(2) 2x  10y = 20
here, let's choose equation (1), and let's represent x in terms of variable y:
x  5y = 10
x = 5y + 10
then we substitute this to equation (2):
2x  10y = 20
2(5y + 10)  10y = 20
10y + 20  10y = 20
20 = 20
note that when you come with this answer (constant = constant), this means that the lines are coinciding, meaning any point can be a solution, because the equations are "equal". if you observe equation (2), we can factor out 2:
2x  10y = 20
2(x  5y) = 2(10)
x  5y = 10
it becomes equation (1).
hope this helps~ :) 
X+4y=8
2x5y=29