X+Y=1
X+(0)=1
X=1

Write the equation
Substitute 0 for Y
Solve for X
The X intercept for equation one is (1,0)

X+Y=1
(0)+Y=1
Y=1

Write the equation
Substitute 0 for X
Solve for Y
The Y intercept for equation one is (0,1)

X-3Y=5
X-3(0)=5
X-0=5
X=5

Write the second equation
Substitute 0 for Y
Solve for X
The X intercept for equation two is (5,0)

X-3Y=5
(0)-3Y=5
-3Y=5
Y= -5/3

Write the second equation
Substitute 0 for X
Solve for Y
The Y intercept for equation two is (0,-5/3)

Equation 1- (1,0), (0,1)
Equation 2- (5,0), (0,-5/3)

These are your points. Now graph them.

(2,-1) is the intersection point, therefore, making it the solution.