Exercise 40 Page 285

Let's begin by verifying that $2^7=128.$ We can do that by typing $2^7$ in our calculator and pressing $\boxed{\text{ENTER}}.$

As we can see, the power equals $128$ which means the equation $2^7=128$ holds true. If we put a logarithm around each expression on both sides, this must also be true because the argument would be the same.