How to solve a system of linear equations when there are less rows than variables?

I took a year off from Math before deciding to major in it, so I'm a little rusty.

I've come to a point in a problem where I have 2 linear equations:

-2a+3b+9c=0

and

-2a+5b+4c=0

I'm unsure of how to solve these 2 equations. I can cancel out one of the variables, but after than, I don't know how to eliminate the next one so I can isolate the value of the 3rd variable. The Cramster expert answer says a = -33, b=-10, and c = -4.

Any help is greatly appreciated.

P.S. I know this looks like a linear algebra question, but this problem came from my multivariable calculus HW where those equations are the equation of the line orthogonal to a plane and the equation of the point on that plane.