ok so you need to find the x and y- intercepts. to do this you simply plug 0 in for x and then for y, giving you the value of each variable.
15x + 20y = 1,800
15x + 20(0) = 1,800
15x = 1,800
x = 120
15(0) + 20y = 1,800
20y = 1,800
y = 90
your x-intercept is (120,0)
your y-intercept is (0,90)