Line $a$ is parallel to line $y=2x+4$ and passes through the point $(2,5)$. What is the y-intercept of line $a$?
Two lines that are parallel have the same slope. Therefore, the slope of line $a$ is $2$. Using the point-slope formula, we get that the equation for line $a$ is $y-5=2(x-2)=2x-4$. In slope-intercept form, the equation is $y=2x+1$. Therefore, the y-intercept is $\boxed{1}$.