what is the y intercept if the equation is g(x)=3/4x

You can graph the function to have that answer. If you aren't sure on how to graph it, then proceed algebraically.

Let g(x) = y. Then, y=\frac {3x}{4}

Then, replace x by 0 (since the equation of the y axis is x=0). You should have your y coordinate. Since you already put x=0, that means that the x coordinate is already 0.

Can you get the full coordinates of the y intercept now? :)