What is the value of a in the equation 3a+b=54, when b=9?

Can someone me with my math problems i have a bunch. i will give brainliest and lots of pleeeaaasssee

Click an item in the list or group of pictures at the bottom of the problem and, holding the button down, drag it into the correct position in the answer box. release your mouse button when the item is place. if you change your mind, drag the item to the trashcan. click the trashcan to clear all your answers. find the lateral area for the prism. l.a. = 0123456789

The equation line of cd is y=-2x-2. write an equation of a line parallels to line cd in slope-intercept form that contains point (4,5)