The x-intercept is when the function crosses the x-axis. This happens when y=0. To find the x-intercept, let y=0 and solve for x.
y = -.75 x + 3
0 = -.75 x + 3
-3 = -.75 x
4 = x
Thus, your x-intercept is (4,0).
The y-intercept is when the function crosses the y-axis. This happens when x=0. To find the y-intercept, let x=0 and solve for y.
y = -.75 x + 3
y = -.75 (0) + 3
y = 0 + 3
y = 3
Thus, your y-intercept is (0,3).