In the coordinate plane, choose the graph with the conditions given.

x + y = 10

We have that
x + y = 10 

step 1
find the x and y intercepts coordinates

x intercept
for y=0
x + y = 10------> x=10
the point is (10,0)

y intercept
for x=0
x + y = 10------> y=10
the point is (0,10)

step 2
graph the equation with the two points obtained

using a graph tool
see the attached figure