A = Allision comes to school
B = Betsy comes to school
C = Chloe comes to school
D = Daisy comes to school
(A∧B) ∨(C→D)
Unfortunatey the argument is not complete so you can't really say that the argument is valid

It cancels out. The best way to see this is by factoring out the x giving you x(3-3) = x(0). Anything times zero is zero, so it cancels out.

By subtracting you want to eliminate on of the variable so that you are only left with one. In this case it would be easier to get rid of the y.
so let multiply the top equation by two and you will get
6x - 2y = 6
7x - 2y = 10. Subtract them
-x = -4
x...

The y-intercept is when the line crosses the y-axis, so when x = 0
y = 3(0) + 6 = 6, so the y-intercept is 6
the slope is 3, as you know y = mx + b, m is the slope

The way you have it written, you mulptiply 9, 18 and 6 to give you 972, then you divide 6 by 12 to give you 0.5 and then add them to give you 972.5. But if the problem is all over twelve then you would have the order of operations. In that case we would
have (9x18x9 + 6)/12. So parentheses...

Area = length times width
so A = lw
A/l = w
48/16 = w
3 = w