I'm just going to give you the answers. You can figure out how they were obtained. Actually the hints are at the bottom of your exercise. You need only juggle them a bit to get the answers.
1]
y = 14 * (7/2)^x This is never going to linear.
2]
y = 32/(4)^x This also is not linear.
3]
y = 5x - 4 This one is linear
If you have a graphing calculator, you might think about graphing these three. The questions are a bit of by guess and by golly. You just have to keep on trying things until you get it. Look at 0 as an x value first.