Hi guys, hoping this is the right forum.

I've got a Maths assignment I'm working on and I've completed the whole paper save one question. I'm really not sure how to go about doing this - here's the question:

5 = 0.4i1 + 1.8(i1-i2)

12 = 2.4i2 - 1.4(i1-i2)

Hope that's readable. I've tried substituting, but that (i1-i2) really throws me off. Anybody able to help?

Thanks in advance.