Substitution Method
Rules on how to engage in the act of substitution:
1. Solve one of the equations for one of its variables.
2. Substitute expression into other equation and solve for other vaiable.
3. Substitute value back into equation.
Example
There are -4 lighthouses on island Rudolph, there are 3 grey per every 100 acres and 4 white per every 50 acres.
On Blitzkrieg island there 2 lighthouses, 1 grey per every 25 acres and 2 white per every 80 acres.
How can there be a negative amount of lighthouses,we need to find out what the value of x and y are to figure this out?
3x+4y=-4
x+2y=2
1. change x+2y=2 to x=-2y+2
2. substitute your new eqation in for the x in the other equation;3(-2y+2)+4y=-4 : -6y+6+4y=-4: -2y=-10: y=5
3. substitute y value in to original problem; x=-2(5)+2: x=-8
Therefore your values are (-8,5)