How to condense into single logarithm
5log base 7 a - 20 log base 7 b

ummm seems that u didnt post the attachement !

for this case we have by definition, if two lines are perpendicular, then the product of their slopes is -1.

then, given the following line:

so,

we are looking for m_ {2}:

then, the line is given by:

we find "b" replacing the given point:

finally, the equation is:

option c