Hello,
1. I agree with Plato that you only have very basic knowledge about powers and logarithms. Therefore you have to learn by heart until tomorrow the content of the attachment.
2.
Now de-logarithmize(?):
Solve this quadratic equation for x. I've got:
x = -2 doesn't belong to the domain of the equation thus you have the solution x = 7.
So you are right - but I really would like to know how you got this solution.