20 more girls $33x+37y=350$ $x-y=0$
Work Step by Step
The second equation can be solved for a variable easily (by adding y to each side, getting $x=y$). This can be used to replace a variable in the first equation and solve the equation. The solution of 20 more girls means that, among the 350 students that there are more 20 more girls than boys taking the course.