A line parallel to y = 4x + 6 passes through (5, 10). What is the y-coordinate of the point where this line crosses the y-axis?
you can find the answer here,
When a line is parallel, the k value stays the same. The k value in this case is 4. but the 6 is subject to change. If you plug in 5 for the x and 10 for the y, the equation becomes 10 = 4*5+b. You can now see that b = -10. The equation becomes y = 4x-10. You are trying to find the x- intercept, so you plug in 0 for x and see that the y value becomes -10. The answer is -10.