Please hurry k-12 quiz

Use the elimination method to find the solution to the system of equations. 2x - 3y = -9 -x + 3y = 6

I'm confused on this could anyone me and show me what i need to do to solve it.

Acaterer charges $500 plus $30 per guest to cater a wedding. walt and traci don't want to spend more than $8000 on catering. write and solve an inequality in terms of the number of guests, g, that can be invited. a) 30g ? 8000; g ? 267 b) 500g < 8000; g < 16 c) 500 + 30g < 8000; g < 250 d) 500 + 30g ? 8000; g ? 250