Answer:
-x^2 + 21x + 3.
Step-by-step explanation:
9x - (x – 3)(x + 1) + 10x
= 19x - (x^2 - 2x - 3)
= -x^2 + 2x + 19x + 3
= -x^2 + 21x + 3.
Answer:8
Step-by-step explanation:12-4=8

The Correct choice is <u>Substition method</u> , as we can directly substitute the value of y from first equation to the second equation.