Let's put together the first and the second equations multiplying the second of them by 2 in advance: we get 5z + 6x = 4.
Now, consider this equation and the third one. Let's eliminate one of the variables,for example, z. We'll achieve that by multiplying the new equation by 3, the third original one by -5. By putting them together, arrive at the simplest equation 13x = - 52 => x = 4. By inserting it in the third equation we find z = -4, inserting x into the second original we finally get y = 6.
+14 
+259 
