Hello,

I don't know which method you know to solve a system of linear equations. So I'm going to show you, how I solve this system:

1. From the 1rst equation you get: a = 3-2C

Plug in this term instead of a in the remaining 3 equations. After a little bit of simplifying you'll get:

b+ 6c+4d = 12

-4b-15c-4d = -27

4b+ 6c+ d = 15

2. From the 1rst equation you get: b = 12-6c-4d

Plug in this term instead of b in the remaining 2 equations. After a little bit of simplifying you'll get:

9c + 12d = 21

-18c-15d = -33

This system is easy to solve. I'll leave it up to you.

The final result is (a,b,c,d) = (1, 2, 1, 1)

Greetings

EB