Answer:
Remember that logarithms are inverse of exponentials. That means the result of the logarithm is equal to the exponent of a power with the same base.
[tex]log_{10} (10)=1[/tex]
Notice that the result is one beacuse [tex]10^{1}=10[/tex]
[tex]log_{10}(10000)=4[/tex]
Because [tex]10^{4}=10000[/tex]
[tex]log_{10}(?) =7 \implies 10^{7} =10000000[/tex]
So, [tex]log_{10}(10000000)=7[/tex]
I would say to thim that [tex]x[/tex] and [tex]y[/tex] are variables of the logarithm, which be solved by imagine the logarithm as an exponential like
[tex]log_{10} (x)=y \implies 10^{y}=x[/tex]
In other words, the [tex]y[/tex] is the exponent and the [tex]x[/tex] is the result of the exponential.