Brian earns twice as much each week as a tutor than he does pumping gas. His total weekly wages are $150 more than his sister. She arns one quarter as much as Brian does as atotr. How much does Brian earn as a tutor?

Let's say Brian gets X amount of money on tutoring.
He uses X/2 on gas.
This amount is $150 more than his sister's wages. Hence, his sister's wages can be written as $(X-150).
What she earns, is 1/4 of Brian's earnings, hence, it can be written as X/4.

Well, you have the sister's earnings expressed into two different ways... equate them!