Ineed to know how to solve this problem using the substitution method for a linear system

The classrooms are trying to raise $1,200.00 for charity. mrs. leblanc's class has raised 50%. mr. patel's class has raised $235.14 ms. warner's class has raised 1/3 as much as mrs. leblanc's class. how much more money is needed to reach the goal of $1,200.00?

Solve the given system of equations. 2y= -x+9 , 3x-6= -15

Write a function for a rotation 90 degrees counter clockwise about the origin, point 0