Draw the line 3x + y = 10 .[it passes by (0,10) and (-10/3,0)
Draw the line y=x [it passes by (0,0), (1,1), (2,2) etc]
Then the solution is the points with integer x and y, that belong to the segment of the line 3x +y = 10 between the x-axis and the line y=x. Those points are (1,7) , (2,4), (3, 1).
