How many solutions does the following system of equations have?
y=5/2x+2
2y=5x+4

one

two

zero

infinitely many

We will use a method of substitution.
y = 5/2 x + 2 
2 y = 5 x + 4   ⇒  2 ( 5/2 x + 2 )= 5 x + 4
5 x + 4 = 5 x + 4
0 x = 0            ⇒  x, y ∈ R
D)   
This system has infinitely many solutions.