The first expression is equivalent to B
The second expression is equivalent to A
The third expression is equivalent to C
You are basically adding like terms. For example for the first expression, it is 7x^2 + 2x^2, which equals 9x^2. Remember since you're adding, do not add the exponents.
6x + 7y = 59...multiply by -4
4x + 5y = 41...multiply by 6
The solution is at what point the two lines intersect.
Plug y into the other equation to get: 5x-4(5-3x)=-3
Multiply it out: 5x+12x-20=-3
Combine like terms and add 20 to both sides: 17x=17
Divide both sides by 17: x=1
Now plug the x value back into any equation to get the y value.
So you get y=5-3(1) --> y=2
The solution is (1, 2)
Cross section of a sphere is a circle
