Could you help me on number 9 on page 70 please? I kept getting a 4.312 answer

Sure. Here’s the problem:

The first thing you should do here is get rid of that infernal :

From there, you can subtract to eliminate the 9*y* terms:

2*x* – 9*y* = 12

– (5*x* – 9*y* = 18)

–3*x *= –6

*x *= 2

Now use *x* = 2 to find *y*:

5(2) – 9*y* = 18

10 – 9*y* = 18

–9*y* = 8

*y* = –8/9

The question asks for the sum of *x *and* y*, so add them up!