Not a function.
Draw a vertical line and you will see that the line intercepts 2 points of the graph.
Log=13
t=4
So, this is because they already given you t because the four is on front of it that gives you your value. From there you will proceed to j7st do the math in your parentheses. You should get log=(1) & log=(13) because 1 times anything is that number just use the inverse of each would be eachother. So, 1x13 is the same as 13x1