Answer:
[tex]10x^{2}-34[/tex]
Step-by-step explanation:
Because we are told equivalent expressions for y and z we can plug those in to 2(y+z).
[tex]2((3x^{2}+x^{2}-5)+(x^{2}-12))[/tex]
Then simplify by combining like terms of the expressions. Values ending in x^2 can be combined with each other.
[tex]2(5x^{2}-17)[/tex]
Now we can distribute the 2 by multiplying each value in the parentheses by 2.
[tex]10x^{2}-34[/tex]
