I'm really bad at logorithms. given the exponential equation 2x = 128, what is the logarithmic form of the equation in base 10?

Sorry to hear that you already took the test. Here is how to do the problem:

2ˣ = 128               
Let's take log base 10 of both sides.
For simplicity, we'll just use the symbol log to mean log₁₀

log (2ˣ) = log (128)                   Remember that log(yˣ) = x log(y)
x log (2) = log (128)                 Divide both sides by log(2) to get x by itself
x = log (128) ÷ log (2)