A(b+ x) = ab+ ax
i cant figure this out

Which is an equation for the nth terms of the sequence 12,15,18,21

Simone claims the initial value and y-intercept are the same thing on a graph. is she correct? if you know that a line has a slope of and a y-intercept of 7, what is the equation for that line in slope-intercept form?

Aline passes through 3,7 and 6,9 what equation represents the line