7x – 3y = 21 Write original equation. 7x – 3(0) = 21 Substitute 0 for y. x= = 3 Solve for x. To find the y-intercept, substitute 0 for x and solve for y. 7x – 3y = 21 Write original equation. 7(0) – 3y = 21 Substitute 0 for x. Y= = –7 Solve for y. The x-intercept is 3. The y-intercept is –7