Answer:
The Answer is A
Step-by-step explanation:
I'm 100% right.
To eliminate x, the coefficients of x's in both equations should be opposite numbers. Since the coefficient of x in the second equation is 3, the coefficient in the first equation should be -3. So she should multiply the first equation by -3.
Answer:
Option C. 
Step-by-step explanation:
we know that
In the rectangle of the figure

so

The constant is equal to 